Do redhooks get dorsal extensions?

[12 Volt Man]

Hi all. I have been keeping redhooks for almost 18 years now, and this latest batch I have has two of them that appear to be growing dorsal extensions..ie the the top of the dorsal fin is growing longer than the rest of the dorsal fin..

I have never seen this on any of my redhooks I have kept in the past. is this common? I will try and post a pic of the fins..

 

[12 Volt Man]

now that I look, its happening on all of them.

here is a pic

 

[Ullopincrate]

I've never noticed that before.

 

[Bogwoodbruce]

Yeah mine have it