Like mentioned, check husbandry. Hot side, cool side, hides, etc. It just helps the rest of us to rule out basic errors like that.
How long had the seller been fasting their animals for?
If the fast was natural, the snake should not be losing any weight. I would schedule an appt with your vet to make sure that there are not any parasites or any other reasons for the snake to be losing weight. I had an adult male fast (his choice, not mine) for about 4 months without much, if any, weight loss.
Good luck!
~jenny
-----
"The python has, and I fib no fibs,
318 pairs of ribs.
In stating this I place reliance
On a seance with one who died for science
This figure is sworn to and attested,
He counted them while being digested."
~Ogden Nash
jenny.thegreenes.org
"If you're happy and you know it,
Bomb Iraq!
If you cannot find Osama,
Bomb Iraq!
If the terrorists are frisky,
Pakistan is looking shifty,
North Korea is too risky,
Bomb Iraq!
