This is my baby Bumi, and he is about 2 months old. He has had this kink in his tail since I got him, sometimes it’s darker than the pictures. I can’t tell if it’s tail rot or just a kink, I have been soaking it in Betadine just to make sure, and I have seen a significant color change but no change in the kink.
It doesn't look to me like tail rot at this point in time. If your cute little beards had tail rot, trust me, you would know. It's pretty noticeable. You can try giving him baths to loosen the shed, or if that doesn't work, try Shed Ease from Zoomed. It really works.