Anyone know what this is?

My kitten (7 months old) has these scabs/rash by his mouth. I just noticed them today, I haven’t seen them before. I introduced another kitten (6 months old) to our home 4 days ago. I got new kitten checked up at the vet today and they said no issues, he just had dirty ears (bacteria and yeast) and cleaned them out and gave me ear drops to administer over the next two weeks…I’m thinking maybe they played too hard or maybe it’s a stress reaction? Anyone recognize what it is?