I can not stress enough how when people need help that it is important to list as much info as possible. Putting up a photo with nothing else seems blatantly rude and lazy to me. If you want someone to help you, then you have to give a little as well. We can't see what your setup is like or know what your feeding schedule is, and these are all important in determining the overall health of an animal. If you would like for us to look over your setup and ensure that everything is proper for the continuing health of your dragon, please include the following info:
Cage Size:
Age of dragon:
Diet:
Supplement Schedule:
UVB Type:
Basking Temperature:
Hot Side Temperature:
Cool Side Temperature:
Method of measuring temperature:
Substrate:
With all of that said, no, it does not look like Tail Rot. Dragon's tails typically darken towards the tips.