Betta Fish isnt eating

Question
OK, so I bought my betta fish awhile ago, about january, and he's been
perfectly fine until about a week ago. He's in a fairly small tank, with glass
colored rocks (large and small) lining the bottom, with one small plastic plant
meant for an aquarium, it's under a gallon, but we try to change the water
pretty regularly, about once a week, and his water was just changed a few
days ago. We don't use a water conditioner because we live in Oregon so the
water's pretty clean I thought, probably a little on the cooler side though, but
like i said nothing has been a problem so far.  He's in the kitchen with planty
of light usually and people moving around him so he's not isolated.  And so
I've been feeding him color enhancing betta bits this whole time, but for the
past week about he tries to eat them, bites for a few seconds, like he's trying
to eat, and then they come back out of his mouth half digested.  Either that or
he keeps them down for a minute or two and then they come back up.  
There's some food on the bottom now, which i'm planning on cleaning up
before it contaminates the water too much, but it doesn't look like he's been
getting any of it down and i'm afraid he's going to starve to death :( do you
know if there's a reason for this? And anything else about what i'm doing that
i need to change.

Thank you!
-Kelsey

Answer
Kelsey,
Anything under one gallon for any fish is considered cruel, please put him into a larger tank/bowl. Also, you should use water conditioner, if there is any chlorine or chloramine in your tap water, it will be harmful to your fish. Lastly, you need to keep up on his water changes. Anything less than one gallon needs to be changed every few days, and definitely not left alone for a week or so. In a two gallon, once a week will be fine.
Once he has a suitable sized home and fresh clean water his appetite should return.