Thanks, that helps ease my mind
All of the above makes sense here. They seem to be happy and healthy (with the exception of the runt who just won't grow). There are many differences between the 2 tanks, and I'm now sure that's why these colors are coming out. The tank they were in had lighter substrate and standard florescent lights. The tank I've moved them to runs about 2 degrees warmer, has a very dark substrate (mostly black), and much stronger lighting.
After getting some feedback, I feel a lot better about it. You've confirmed what I'd hoped.

Thank you!