Jacksons are susceptible to edema likely caused by too much prEformed vitamin A... and reptivite has that in it so I would only use it once a month.
I would recommend that you feed the crickets a wide assortment of greens (dandelion greens, kale, endive, escarole, collards, etc) and veggies (squash, sweet potato, sweet red pepper, zucchini, etc) and a bit of fruit (berries, melon, apples, pears, etc).
Increasing the basking temperature a couple of degrees might make him eat more.