Bare with me kind of long but help!!!

My daughter is 3 months old & just developed this yeast rash. We were seen by a nurse practitioner because she has been having that & loose, seedy, mucus stools. (Apparently tested positive for blood in stool?) Which could be from having loose stools also, but they changed her formula to nutramigen.. she won't drink it. Something about milk I can't remember which wording for milk issues.. but she isn't really all that fussy ever. Gains weight fine. Doesn't cough or anything, no spitting up much. (She spits up a lot more with nutramigen when she would take some) my question is, would I be able to use the getber pro sensitive for lactose sensitivity because nutramigen tastes horrid. Otherwise I seen gerber HA or something but I just want her to eat and poop normal. We have just gone back to the soothe tonight so she can at least eat until the morning when I call her Dr. I just don't always trust them either. Because she has no issues on it besides loose poops hard time going & all that I already said. Thanks for reading.