There's a phenomenon known as "the wall" which many (but not all) ball pythons experience. Somewhere between 600 and 1,000 grams, ball pythons decide it's the perfect time to stop eating for a while - sometimes as long as a few months!

It's not always that they are going off feed for breeding, but an 850 gram mojave male is pretty much big enough to breed - so that is also a possible reason.

I wouldn't worry too much, even if he does stop feeding for even longer. This time of year it is not that uncommon. As long as he doesn't look too much weight, or start to look noticeably thinner and skinnier, you shouldn't have anything to worry about.

-Jen