They are adorable!!!
I can suggest only a couple things.
I think it would be best to choose one food and not keep switching them. I have not heard of Halo but my son feeds his furbaby Blue buffalo and he does really well on it. (My Charlie has to eat a special diet)
Charlie is as you called it "free fed" I leave his bowl out all the time and there is always food in it for him however Charlie is trained to go potty outside and I always let him out at 10pm and he is good then until 6am. If you dont want to crate your babies at night because of possible poo
you might try pulling the food up at 7 or 8 at night and let them out at 10pm then they wouldn't be able to eat late and then have to poo.
Their weight doesnt seem to me to be an issue and if the vet hasn't shown any concern I think you must be doing fine.
Other members will have more/better information on types of food but choosing one is going to be the best