Just remember, when you switch the babies to the new milk, do it gradually, not all at once. Give them 1/4 new milk, 3/4 old formula for 1 day or two, the next day 50/50, keep it 50/50 for a few days, then 3/4 new to 1/4 old, and finally, 100 new.
I cannot tell if the mother was feeding them or...