I do mix for my gal, for 120ml of milk, I use normal temp water of 100ml and hot water of 20ml. its best to consume milk when it's done and I will throw away after an hr if left unconsumed. I have been giving her biogaia ever since 3 month old when ever she has diarrhea or constipation till now. didnt change her milk brand since newborn.
Might be good to change formula. Mine drank goat milk after birth and took to it very well, but was suddenly very gassy in the second month. it only improved after we switched to similac alimentum. So it's good to try different brands to see what works.
Try changing to a different formula milk