What Is The Bump Behind Leg? Appearance Changed. Why Does It Turn Bright Red?

My daughter had a bump behind her leg that started out looking like a skin tag, then, a few months later, it looked more like a wart . It changed appearance again and looked like a skin tag. She now has two behind her knee and a few on her upper leg and now a small patch of them on her lower abdomen. The original one is now very red with a whit head (like a pimple ). Should I be concerned? She is 2 years old, 19 pounds, and has asthma . She also struggles with diarrhea and we give her miralax once a week to help her with that. Recently she her bottom has turned bright red when she has a loose stool. She screams and cries when it is time to change a poopy diaper.