Before considering moving him, I would have a chat with his key worker or a manager and say he’s getting very sore and needs his nappy checking/changing more often than they are doing. We had a similar issue when my daughter started nursery and after a chat making it clear that I really wasn’t happy that she was getting so sore, it’s never happened again. We don’t get many art things or cards sent home from nursery, but their policy is not to make a child do something they don’t want to, so my assumption is just she didn’t want to do an art thing.
I would talk to the director also do y'all have an app they use to track diapers? My LO was coming home with diaper rashes all the time and the teacher said she didn't update the app all the time and her diapers were missing enough when I counted so I thought maybe she was right. After a while I got tired of it and switched to her to a new daycare. And she never had another diaper rash after. Her new teacher had 4 children of her own and she treats every child in her class like they are her own. She actually takes a stand for the kids in her care. I had found out my LO was allergic to milk and eggs and the director said I would have to supply food and milk from home. Her teacher just gave her water instead of milk and anytime they had dairy or eggs in meals her teacher kept other things in the class for her to eat and offered them to the other children as well to keep it fair.
My sons on Movicol, he’s not in nursery but he is prone to a sore bum from time to time if it’s not changed immediately. My son can do the toilet on the way to the car from the house 3 steps away unfortunately there’s no way to prove the nursery haven’t done their care if your not checking his bum before leaving their care. Not sure if it’s the same where you are but some of the nursery’s in my town you have to pay for them to bring home their pictures and cards maybe put this question to them. Even suggest they initial the paper before getting the kids to make their crafts so they can’t get jumbled up.