Sounds like if you don't act fast you'll lose it. Agree with ivan3 --- they can fade fast for no apparent reason.
What color is its faeces, assuming it's done some you know for sure is its? What consistency? If it's not pooping at all then it's been in this state for a while and the person you bought it off should be contacted for a chat and maybe even a refund, if it was like this when you bought it...
If the poops' 'white' is bright yellow with a khaki green 'dark', if any, and it's liquid, then it's blackhead; that's one severe disease you can easily diagnose by faecal color and consistency. Advanced at the stage I described it; the poops gradually attain those colors and liquidity as the disease progresses. Once blackhead is far gone they sit down all day, don't eat, and may drink water at the most, but not often. The cure is a cup of unpasteurized, unhomogenized (raw) cow's milk with the fat skimmed off the top, mixed with a flat teaspoon roughly of preferably raw honey. Works the majority of the time. But I don't know that your turkey has blackhead, just a random suggestion that may or may not be helpful. Maybe only in future. Helps to know what kind of poop it's doing.