It got cooler so he figured it is fall and time to get ready for winter, they do that at that time of the year, not eastivating, just resting. It is normal. They sleep with their eyes half closed. Also as they get older they eat less frequent. Mine can go every 2-3 weeks at that time of the year, if they got lucky and one of the snakes refused mice, then they'd go even longer then that.

at 6 months he should be close to his adult size and just crickets are not enough, you should move to nightcrawlers. Just watch him for anything out of ordinary, if looks healthy, less frequent but eats, poops, all is good.