After examining the tail afterward I think it is because blood wasn't getting to the whole tail. Now that I think of it my younger cousins were at my place and they might of put the cave on top of it or something when I was gone. I will talk to them.
Pumpkin lost part of her tail when I first got her. (May of put cave on tail).
I didn't but anything on it. Kept a close eye on it and removed anything that might bother it. I also fed her crickets one at a time and removed the last one if she didn't eat it so they would not nibble on her tail. And I kept the habitat extra clean.
Grew back in about 6 to 8 weeks. Can barely tell she lost it.