It's probably the powdered goat's milk. This will not be enough nutrition for them to survive. Please go buy Powdered Puppy Esbilac formula, at pet stores, feed stores and sometimes Walmart. It has to be powdered not liquid in a can and has to be Esbilac (not petlac or other brands) This formula has a long successful record and others have caused lots of health problems.
Please visit this site for basic squirrel care:
https://www.henryspets.com/baby-squirrel-care/
Read all six pages and follow the instructions for housing and feeding tools for best success.
Babies should be eating -5% of their weight in grams. You MUST weigh them to determine how much they should get. Overfeeding can cause diarrhea, underfeeding causes many other problems. A kitchen scale from Walmart or store that sells kitchen items is usually under $20. Also, keep a record in a notebook so if there is a problem you can look back and it may help you find solutions. FOR EXAMPLE: If baby is 80 g multiply that by 0.05 for the amount to feed at each feeding. 80g x 0.05 = 4 ml
We recommend using a syringe and nipple, not a bottle. The smaller the syringe the less chance of aspiration into the lungs so stick with a 1 ml syringe and graduate to a 3 ml syringe when you feel ready and they seem ready to master it.
At this age you can feed every 4 hours morning to evening with no middle of the night feeding as long as they are healthy. If you are working with sick or compromised babies they may need middle of they night hydration, etc.
Welcome and best wishes. Happy to help anyway we can.