Those are such pretty boys!
It does look like a fin injury. If they have been growing back fine until now then (1) they have reinjured the fins, (2) they have fin rot, (3) a combination of the two.
I don't have much experience with fin rot, but I know there is a treatment for it written by our resident soon to be veterinarian, Darkmoon...on the diseases thread under betta care section, there are 2 stickies of common diseases and treatments...
(1) I would start w/ aquarium salt 1 tbsp per 5 gallons.
(2) change 25-50% of aquarium water, put in water conditioner.
(3) use stress coat as directed on bottle...this is to help fins to heal.
It does look like a fin injury. If they have been growing back fine until now then (1) they have reinjured the fins, (2) they have fin rot, (3) a combination of the two.
I don't have much experience with fin rot, but I know there is a treatment for it written by our resident soon to be veterinarian, Darkmoon...on the diseases thread under betta care section, there are 2 stickies of common diseases and treatments...
(1) I would start w/ aquarium salt 1 tbsp per 5 gallons.
(2) change 25-50% of aquarium water, put in water conditioner.
(3) use stress coat as directed on bottle...this is to help fins to heal.
