Why is he so small?

[aLittleLessButter]

Bath her in an electrolyte bath, don't resort to feeding the small prey constantly, after a while it will go for what you are trying to feed it, try braining the prey item, double and triple check your husbandry and even change things around in the tank, it may not feel comfortable with how things are, regardless of your husbandry. There are tons you can do to change a picky eater. Mine was about 150g at a year, she in now 3 months older and nearly 300g.

He is in a rack with back heat controlled by herpstat4 which also controls my other 2 racks. Hotspot 90 ,cool side 81, humidity 60. Blue shop paper towel substrate. He has 3 hides among other things ive added to make his space a little more cluttered. I've tried a few different things; different hides, more clutter, changing which slot on the rack he's in. All changes were made weeks apart from each other to prevent stress. No matter what the change, his habits are the same: on for 3 weeks, off for a month. I tried bathing him once as recomended by someone on here but didn't make a difference. Many say bathing is more of a stresser anyway so I avoid it. Not sure what you mean by "electrolyte bath".
I have 7 balls total which I've had for a year, all doing great. Everyone eats every week except for my clown