Here are some thoughts from experiences I've had to consider and see if any of it might fit your situation. Working on limited knowledge but going off what you've posted just above, here goes:
If you are in the middle of this problem between your dogs because there is possessiveness involved, that is something you can work to stop but you will have to make some changes and also determine which one is guarding you and doesn't want the other to have much access to you. Who knows what made it start or how long they lived in peace together and who really cares as you have got to fix it by taking control of the situation and not letting the dogs run the show. If Wyatt is doing the growling, he's probably the one who is so possessive but not necessarily. He could - could - just be reacting to the other dog's signals of "She's mine - don't you come near while I'm here" and growling back at those and getting tense. His tension tenses up the first dog and more signals are sent and you soon have a fight over mommie.
No matter how well your little guys are already trained, I would start and at all times enforce the
Nothing In Life Is Free program for everything for a few weeks, right down to even their water for the first week but everything else for a few weeks after that. Get them obeying a command for everything they get or do. It's a marvelous tool for doggies acting out in any way. I would stop the dog lying next to me when the other is around until they are farther along in their rehab from this present unstable state. Make them lie on the floor or in their beds for a time and treat them for staying in their beds.
I would obedience train each of them x3 daily for 5 mins. each session, giving big treats and smiles and praise for each accomplishment no matter how many times they have done the tricks and get them working with you one at a time and then together. Good working sessions help give a dog structure and enjoyment and confidence in his own worth and achievement, not to mention teaching him to do what you say quickly to get his praise and reward.
Desensitize the trouble-maker to your playing and loving on the other dog. Put the very possessive dog in his open wire crate and sit down next to it with the other dog and play with that dog right there on the floor by the crate, all the while tossing a juicy piece of chicken into the crate every time there is physical touch between the dog you are caressing and playing with. Don't worry if the one in the crate becomes agitated by this or growls at first as this activity goes against his possessive attitude. Ignore this for the present and allow him to slowly come to accept the interaction over time. Keep the sessions about a minute or two long at first and then allow the crated dog out, put the other dog in the crate with a treat. I would let the just-freed dog outside to pee, decompress and run off any pent-up frustrations and stay outside to play and explore a while. If you can manage it, a fast walk would be good at this time to kind of work and then relax him. Bring him in the house for water and a good rest and allow the other dog now to go outside to pee, play and walk if possible. By the time these two are back together, they should have their frustrations worked out for a while, be pleasantly tired and ready to co-exist peacefully for a while. For the present, don't let either dog lie next to you but in his bed on the floor with the other dog.
I wouldn't let one or the other next to me for a while during this training until you have gone through the desensitization exercises for about two weeks and prolonged the playing sessions with the non-jealous dog while the jealous dog is in the crate watching as you play and getting his treats when physical touch occurs between you and the other dog.
In time, the jealous dog can then be moved out of the crate on the leash and told to lie down and watch as you play with the other dog and toss the little possessive one a treat every so often. Watch his body language and if he begins focus, alert, get tense, growl or get agitated, stand up and tell him "No" with your hand held out in a stop position in front of you. Stand there over him making constant eye contact until he backs down and calms down, even putting the other dog in the crate while the little growler settles himself back down. But stand there calmly until he does. Take deep breaths and never get angry. You are watching a baby boy learning to accept changes and it is hard for him and he needs time to work through it. When he does settle, sit and obviously watch him for a while, catching his eye and then treat him and bring the other dog back out and resume the play, treating little Mr. Possessive all the while but letting him know you are watching him.
Little by little you should be able to show the possessive dog that you are in charge of their interactions, that play with the other dog is highly rewarding for him because Mr. Jealous is treated frequently the whole time and you will not allow him to growl and takeover control. He'll be used to obeying you because that obedience training and NILIF work that you will be doing concurrently during these weeks will all the while be conditioning him to always do what you say quickly and to learn to love obeying you.
After a two-weeks' time, you should be able to allow the other dog to lie next to you for brief periods while you toss treats over to the jealous dog and then praise him, let him outside to potty, play and release his tensions and then switch the two out, letting the other dog out for a while.
Next teach Widget to lie quietly by in the crate as you play with toys with Wyatt, treating Widget with treats tossed in the crate and following the desensitization training above. Do not allow Widget to feel he has control of the toys any further now that fights have happened and allow him to slowly learn that the toys are yours and as pack leader, you and you alone decides who plays with them when. With fighting dogs, it just has to be this way. Some never really do come to accept toys being played with by the other dog or dogs if the pack leader isn't really in control and it is always a problem. But if you are gentle but very firm and slowly decondition them to owning toys themselves, Desensitize them to seeing other dogs play with toys they had thought were their own and on board with playing by your rules, they will submit to that situation in time. I've seen it work time after time.
With most dogs, this type of intense training and desensitization sessions work together to teach them who is pack leader and in firm control and is taking the time to teach the trouble-maker how to accept his pack mate in a way he'd come to strongly dislike. He learns that he doesn't have the place of authority in your pack and he can't make those kinds of decisions and dogs are readily able to change and love a good, strong, loving leader. Dogs are genetically programmed to accept hierarchy and thrive on it so don't be afraid to take and hold control. Sometimes with boys(or even girls) it is just necessary!!!
