Help caring for a starved betta?

[JKfish]

I just got a beautiful but tiny yellow delta from petco, and right now he's in a large tubberware, under observation.

The poor thing looks like he's been starved, and his fins clamped to his side (I almost had a heart attack when I thought he was missing a pectoral fin). He's stressed, and has lost a bit of color. He doesn't move much, and stays at the bottom of the tubberware. However, apart from that, he's in good shape. In the petstore, his colors were beautiful, and his fins are in great shape, no tears or finrot. I don't see ich on him either.

However, the only thing I've noticed looks a bit wrong, is body is sort of curved (barely noticeable), and he isn't sitting straight, but rather leaning a tiny bit to the side.

I've fed him one top fin betta bit, I don't want to feed him more, because I'm afraid he'll get constipated. Any advise?

edit: now that he's eaten the pellet, he's taking more interest in the world around him, and swimming short distances every now and then. :)

[RandomFish]

Hi! I have a betta who was starved too. 1fish2fish recommended New Life Spectrum Growth formula and bloodworms to put some meat on his tiny little bones. So I ordered some New Life Spectrum Grow on ebay and the jar is HUGE and took forever to get here. Would you like me to mail you some? I know all my bettas combined will never be able to finish the whole jar. I'll send you some free of charge, just PM me with a mailing address if you want it.

[JKfish]

:D Wow, thanks~ I'll have to talk to my parents about it so they won't be confused if a bag of fish food arrives in the mail, but once I do, I'll pm you my adress. :)

[RandomFish]

lol ok. I hope they'll be convinced that it's fish food and not drugs. ;) I'm pretty sure they'll be convinced once they get a whiff of the fishy smell haha