Bettas, that's normal for that color platy. :) A lot of gold or pale colored platies or other fish have red spots where the gills are because the tissue is very thin right there. The gills get a lot of oxygen and turn really red and show through.
I'm pretty sure Dinah has a cold. She keeps making squeaking sneezy sounds and washing her nose. Looks like it's off to the vet sometime this week. Don't know when, don't have a ride until Thursday. Unless the small pet vet works late tomorrow night. :/ Shoulda known I'd get a sick rat from Petsmart. Probably will take Delilah too, since they are sharing such a small cage.