Help With My Old Betta!

[Ficious]

my old guy was put into a bigger tank today....taken from a 3 gallon to 36 for a lazy retirement...first couple of minutes he was fine swimming around but then i noticed his fins all loose and he was dive bombin straight to the bottom. his spine looked curved. i just grabbed him with my hand and took some water from a diff tank to put him in. IMO he seems better..hes in a small clear bowl....whats happened? i acclimated him over 30 mins and slowly adding smal bits of tank water in.

any ideas??

im going to do some tests when i get back from the fish store, thanks guys

 

[WILDER]

How old is the betta as the spine can bend with old age.
Other reasons why the spine bends is old age, injury, birth defect, internal parasites, fish tb, vitamin defiecency.