Well, he stopped eating, so something you changed made him uncomfortable.
Maybe you had some new visitors over, maybe you watched TV too loud, maybe you left the light on in the room too long, maybe you got a new pet and he doesn't like it, maybe the stars are aligned the wrong way... Think about the past two weeks, and see if you started doing something different in the room the snake is in. That may have been what triggered it...or maybe the snake just doesn't feel hungry this month.
75 gallons is a little excessive for ball pythons. They do tend to do better when kept seperately, and in a relatively small cage for their size. A 40 gal breeder tank is usually more than enough room for an adult ball python.
This IS the time of year for a lot of balls to go off feed. A couple missed meals is not too big a deal if the snake is a good weight (looks nice and round) and not losing any noticeable weight. So, your ball is probably going to be just fine. I'd scrap the 75 gallon for the balls, and invest in them each getting their own cage, and just wait out the older snake. Don't handle it until it starts eating, which will probably be anywhere from a week to a month from now. I repeat - as long as the snake isn't noticeably losing weight, it's not a bad thing if it's not eating.
Obviously, double check husbandry (temps, hides, fresh water, etc), and don't handle the snake until it eats. Handling can be a stressful event for the snake, so it's best to eliminate possible stressful things until the snake is eating again.
Good luck!
~jenny
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"Polysyllabism in no way insures that what you're saying is actually worth being heard." - Blake (an e-friend of mine)
"I have never made but one prayer to god, a very short one: "O lord, make my enemies ridiculous." And he granted it." - Voltaire