Feather duster mangled feather

[baronen]

My feather duster has two newly bent/mangled feathers (what are these actually called?). Two questions, will these grow back? Also, what could have caused this?

 

Evo 13.5

firefish

two sexy shrimp (always hanging out around his tube base, occasionally annoying him to the point where he retracts)

porcelain crab 

[Pjanssen]

The crowns of the dusters can completely fall off if the animal is stressed by either water quality or a fish or crab that is bothering it. They will grow back if conditions improve. They need to be fed some kind of phyto or plankton daily.