3mo formula changed from Similac Sensitive to Enfamil AR. Wet stools/diarrhea, awful diaper rash, & very pale yellow-green pasty stools. Milk change?

That is possible . stools expected to change w/formula change until your baby's intestine adjusts to new formula. Greenish yellow seedy stools are a normal stool color for babies. There are many. Is the baby excessively fussy /gassy. If not, give it a bit longer to see how your baby is adjusting. Many changes & you can't tell what works. for rash-barrier ointment & air helpful can mix maalox w/it and apply.

Related Questions

My one year old just started cows milk. I noticed he does fine with 2% but got horrible gas pains, loose stools and bad diaper rash. Why is that?

Question incomplete. Please rephrase. You've asked us to compare your child's response to 2% milk which you say is well tolerated, versus...What? Which causes gas pain, loose stool, etc. Read more...
Confusing question. You don't list what s/he drank before: bm/formula, if formula was it soy, lactose free or cow milk based. The symptoms sound like simple lactose intolerance, and deserves a discussion with your doc. In the mean time a trial on lactose free milk (lactaid) could improve things until you do. Read more...