[LebronTheBetta]

I think you are now seeing the inside part of your fish. I am sorry for the sickness. He had Fin Rot before, right? Are you sure it was fully healed? If the Rot is finished with the fins, it would next go to the body. I have never before seen this kind of sickness, so forth, I do not know the cure. If your trying aquarium salt, see if it actually worked.

 

[LebronTheBetta]

There is a post on this type of thread that this Blue Betta may have. It is called,
IMPORTANT: Watch for these Disease Signs.
I read it, and it mostly strikes Blue Betta Fish. Read the Symptoms, and if it is what you have, keep on reading.