How old is your Jacksons? If he's closer to adult age (8 months plus), it might not be that big of a deal. If he's younger, you may want to fill out the "How to Ask for Help" form to see if we can troubleshoot any issues that might be contributing to a loss of appetite.
My Jax has always been a snacker. He might one or two bugs first thing in the morning and then he might eat one or two later in the day, but he does not "pig out" at any one time.
He won't eat every day either - about every third day, he is not interested, so I generally skip a day if he has eaten the previous two. I will try to feed him something dusted in the AM so I can be sure he is getting his calcium, then will free range a few bugs in the cage for him to hunt down. It's good enrichment. Ferdinand has always been rather small, even for a Jax, I think. At 2-1/2, he is about 65-70 grams.
How do you mean "Firing Up"? My Jax will get excited and puff his chin and rise up on all fours to hunt. I think that is normal.