FWIW - I have no idea what the issue is with the red fins on your fish, but I have a big pike and he developed red fins and skin blotches after a rescaping of his tank. I thought it was some stress reaction to the change. I never did figure out what it was for sure, but a few weeks later I treated the tank with Kanaplex for something else on a different fish.
The red fins and splotches cleared up over night. I'm thinking is was actually septicemia.