Yesterday I came home from work to find the latter half of Haku's tail turned black. It's been almost a full day and it's still like this, despite no other stress marks on his body. He's about four months old, his temps are perfectly in order, and I just upgraded to a Reptisun 10.0 UVB tube (currently on top of tank but I'm getting stuff to mount it inside this week). For the past two days he's been refusing his insects (crickets, occasional superworms, and the rare hornworm) but he's been absolutely crazy about his salad so I've been dusting calcium powder on that. Here's a picture of what his tail looks like now. Sorry that it's weirdly rotated but I can't seem to make it upload normally. Any idea what's going on with it?
His tail looks normal to me so I wouldn't worry. It's common for their color to change along the tail and it can be caused by several things. It could just be mood, or it could be that he's just darkening to absorb a bit more light. I see their tails darken like that regularly so it's pretty normal and not necessarily a sign of a problem.