Betta Fish: Half year Transformation (?)

Is it just me worrying too much or is his tailfin not growing as pretty as it could? pic 1 is from when I got him like half a year ago. Im regularly checking water parameters and changing water at least once every 2 weeks,, he is in a 50L tank with only pygmy corys as tankmates. Also I swear he knows when Im pulling out my camera for a picture he never stays still when I try to get a clear shot of him with his fins fully stretched 😂