argh... yup, that's what my HMs look like. I just found out one of them was scared by the flower next to his tank. I had put a Christmas cactus there for him to look at and feel like he had more plants, but when it bloomed - HOLY COW! His tail disappeared! I just realized yesterday the timing and moved the plant, and today his tail is starting to smooth out.
I bet it'll come and go. He's probably just stressed out. Give him some places to hide until his decorations come in. Maybe a mug put sideways? Maybe he just feels like he's living in a fishbowl! o_~ :)