He's always had a darker tail end since I got him 3 months ago (he's a little over 7 months) but he's really lightened up in the last month but not his tail. The tail has shaded but doesn't really get lighter. He still feels it and moves it and eats very well. Is his tail just normally dark or is it tail rot?
This doesn’t seem to be tail rot. I’ve seen this before, and it hasn’t been tail rot. If you feel comfortable doing so, you can post more pictures of his tail, then the answer will be more clear. For now, I wouldn’t worry. Just keep us posted.
I agree that looks like normal coloring. The darker end of the tail is fairly common. It does look like the tail was nipped and damaged at some point, but it looks healed over now and isn't likely to cause any issues going forward.