Whats your substrate?? (your sand/gravel)
If thats too sharp it could be causing that. Also apparently plastic plants tear them up too.
Also, check to make sure he's not snagging himself on the new water bottle filter addon, as it may have a sharp edge.
The gravel is not sharp at all if you want to take a look at it here is the
link ,its hard to tell in that picture though. I don't think he would be able to get to the bottle, but just to be sure how would I dull that? I have one plastic plant and the are are silk, I'll take the plastic one out if that will help. It seems to be running all down him tail though. Just to be sure I cleaned his tank with a gravel vacuum (I removed more then 50% of the water) which was very helpful and it got a lot of grime. Then I added some product that would help the regrowth of his tail.