Baby formula

My 4.5 month old has a very sensitive stomach. I tried to exclusively breast feed but she hasn’t been gaining weight as she should due to a ( we think) tongue tie. Her pediatrician wanted us to supplement my breast milk with formula to help her get some extra calories. We tried similac neonatal and she broke out in a rash. We then tried alimentum which makes her very constipated.

She’s getting her tongue tied released soon which we hope will help with latching but for now what is a good formula for sensitive babies we can try ?

She’s also seeing a GI doctor , ENT doctor , lactation specialist, chiropractor & CST doctor to see if there are any underlying issues.