My twins are getting over the tummy bug, but now my boy twin has this rash on his belly and chest. Looks like it might…

My twins are getting over the tummy bug, but now my boy twin has this rash on his belly and chest. Looks like it might be on his face too. I know it's hard to see but it's the best picture I could get. I use free and clear detergent. But it could be his shirt? Never had this before. No fever either. Not on meds. Has doctor's appointment tomorrow. He just got back from baby sitters. Said he barely ate