Sounds like a yeast infection which, for babies can be caused by sitting in a wet or poopy diaper for too long.
We're pretty vigilant and quick with the diaper changing, as is our daycare center (they log every diaper change, post the time, and tell you if it was wet or bm - your center should be doing that). We are also totally proactive when it comes to preventing diaper rash. However, our son still got a yeast infection recently.
I wouldn't go into a panic or yank her out of daycare, but what I would do is take her to the doctor to have him/her take a look at the rash and see if it is a yeast or other infection. You should also understand that with babies and especially girls, yeast infections are pretty common whether they are at home, at in-home care, or a daycare center. Think of all the nooks and crannies in the folds of the vulva where moisture can hide and spur on a yeast infection. You're not a bad parent, nor are you doing anything wrong because your child has a yeast infection.
You're paying the daycare to care for your child - if they aren't changing your child enough during the day, voice your concerns to her teacher or the center manager. Anyone who changes a diaper should wash their hands first, put on gloves, change the diaper, remove gloves, then wash hands again. Ask if this is the practice. Also, I highly doubt they will 'air out' your child for extended periods of time. Imagine how unsanitary that could be if your daughter pees while airing out.
Good luck to you!