Unfortunately that's likely to be what is going on here. Young corn snakes can easily lose their tail tips this way, & while it may appear to be some sort of "scale rot", I wouldn't be surprised if the tail tip falls off with the next shed. I really hope the OP keeps that vet appointment, because a snake losing a tail tip is actually much more of a concern that a little yellow coloration on their scales.
JPNLKT: The tail tip soaks may help to loosen any unshed skin there, plus the antiseptic use may help prevent infection if there's any skin breaks, but be VERY careful about removing it. Also, it's better not to use Neosporin ointment (or use VERY little) as it tends to mess up future sheds- a better choice is Vetericyn ointment made FOR reptiles- it's water-based, not petroleum-based, & won't mess up their scales/skin.