Bearded dragon need help!

I have a 7-8 month old bearded dragon im not sure of the sex yet. i bought him 3 months ago from petgoods, he had a nipped tail. The people there said it healed fine, but the past couple days ive noticed that the end of his tail is really dark. i have all the lights you need a beardie and calcium. i just dont know whats wrong or what to do......... heres a pic.

https://mail.google.com/mail/ca/?ui=....1&disp=thd&zw

The picture did not work, however are you sure he's not just getting ready to shed? Beardies shed in pieces, and I know mine gets really dark patches a couple weeks before he sheds.

Thanks im hoping thats all it is