I went through a year of my puppy not eating dog food. I cooked for her and gave supplements also. I did find that when I cooked for her she would still kind of pick through the food but when I gave her leftovers she would turn away from it. When I started reading about grain free foods I started substituting sweet potato for rice or other grains. She loved it! I would cook chicken or beef and frozen veggies that i would microwave and then put through the blender before adding to the meat and sweet potato mixture. It was a big hit and I have to say I felt a whole lot better feeding her sweet potato over grain. I kept her on supplements. Although I knew she was getting pretty good nutrition I still wanted her to eat dog food. I finally found she loved Stella & Chewy's freeze dried food. I now mix it with Nature's Variety grain free food. I think it is a combination of two very healthy foods and she is doing very well on it. I have to make sure she never gets any human food and no snacks before she eats her regular meals. Having other family members in the home sometimes means having to be the food police.
Have you checked her teeth? If there is something bothering her in her mouth it may keep her from wanting to chew kibble.

If she will eat more at each feeding could you just increase her amount?

I homecooked for awhile. This recipe would not be fed here either.

Avoid garlic whenever possible.
Balance the supplements - you are probably missing calcium too.
Too many vegetables for a dog losing weight. Not calorically dense enough.
May be lacking fat.
Your pups are being underfed.
Whitefish is okay, but not great for weight gain.

A board certified veterinary nutritionist is needed. Anybody can call themselves a nutritionist, but that means nothing. Very few vets know how to properly balance a diet. If this isn't working out, probably time to try dog food again..

Have you had an ultrasound to check for cancer? My old cat had cancer which caused him to drop a lot of weight dramatically and he lost his appetite. The same thing just happened to my neighbors with their dog. She had cancer and in this case the placement of the cancer made her stomach look bloated/enlarged and she lost her appetite/couldn't digest the food.
If you have had an unltrasound then I would just concentrate on higher calorie foods that are nutritious.