Bettas fins look almost cut in half

[AvoidablePie6778]

My betta fins have slowly changed color and then suddenly a few days ago they seem to have been cropped almost like someone had taken scissors and just snipped them in half. No this absolutely is not how it happened. I am trying to find out why and what to do. He is in a 5.5 Gallon tank temp 78. 7, readings I have a 5 test strip gh, kh, ph, nitrite, and nitrate. Readings in same order: (admittedly gh a little on the higher side) 60, 80, 7-7.5, 0, 20. Ammonia is 0 checked frequently. water changes weekly at 25% snail as tank mate, had thought it died after month long hiatusand recent removal of decorations that were not good in the tank, which oddly none of my decorations have done well in either tank and don't know why. I use prime, stability, and pristine in water changes. Has sponge filter. 

[Colu]

Is these anything Sharpe in tank that could have cut his fins any Redding to the edges of the fins is he eating ok @AvoidablePie6778

[nabokovfan87]

It's very difficult to see much given the lighting and blur on the photos.  I would look into fin rot and compare that to what you see in person.

[AvoidablePie6778]

There is nothing sharp in the tank I've gone over every surface of anything in the tank with my hands to ensure nothing could snag a fin. Eats totally fine. It doesn't look ragged or frayed so unsure if it could be fin rot. I've tried getting clear photos of my two boys but they are very difficult to get a clear picture of for some reason probably my camera lens

Edited January 16 by AvoidablePie6778
To add photo info

[nabokovfan87]

Hm.  The shrinkage could be a sign of fin deterioration / fin rot.  Do you see any sort of white edges on the end of the fins?