There are many reasons for Balls to go off feed.
1. Overfeeding - too large or too quickly (this usually fixes its self after they miss one or a few meals)
2. Husbandry issues (check all your temps, humidity, hides, etc...make sure everything is correct)
3. What I feel is the biggest - breeding related changes (climate changes - lighting, temp, etc.) can cause balls to stop feeding while they look for a mate). This is the time of year when Balls breed so we see a lot of snakes stop feeding for awhile.

But each snake is different. I have some breeders who never miss a meal, I had others that hadn't eatin since November but are starting to come back on feed.

As long as they are healthy and not losing weight I wouldn't worry about it.
(Just be sure to check #2 to be sure )