Diaper rash and daycare

My daughter started a new daycare last week. Tonight when she got home she was dry so I didn’t change her as usual and after dinner still dry. I was getting her ready for her bath and noticed significant diaper rash on her vagina and her butt. She couldn’t have been wet for very long tonight. How long does diaper rash take to show up? I’m concerned the new daycare isn’t changing her enough and that’s what caused this. She was fine this weekend and this morning. The only other time she had bad diaper rash was when she had an ear infection and was on antibiotics. Anything else that could cause it? It just looks so painful. I feel like such a bad mom 😢