Off brand formula

Anyone had their little one be allergic to off brand formula? My daughter is on target brand formula and she keeps breaking out in a rash… I had her on target brand of gentlease and she broke out in a rash on her face, so I thought it was a milk allergy so then I switched her to target hypoallergenic formula and she’s still breaking out in a rash… all in between these 2 kinds of formula I had samples of enfamil sensitivity and nutramigen .. she never broke out on either of those. So could it be that she’s allergic to off brand formula?