How much to feed 4 week old puppies?

I have seven 4 week old puppies that I'm fostering that have been eating gruel since 3 weeks old (bc mama has mastitis and cannot nurse). They eat it up quickly and i always end up having to make more every time they eat (3x a day) bc they lick the plate clean. I think they probably end up eating 1-2 cans of canned food per feeding (I mix canned food with water, esbilac, and goats milk). Their bellies get very round after they get seconds. Should I just keep feeding them more until they stop eating on their own? I'm just confused on how to know how much to feed them, especially bc we don't know their breed so can't calculate their adult weight