Dart Den

I have had quite a few albino tads from my Banded group and they always develop a buoyancy problem and die before morphing out, yesterday I was feeding frogglets and noticed that one of my bandeds is much darker than the others. I have never had a melanisitc froglet of any species so I am not sure if that's what I have here and wanted to see what everyone thought. Melanistic or just a dull frog? Also has anyone else had a group of frogs throw albino and melanistic offspring?

Chris