Entomology enthusiasts: Strange cricket demise question

I have 4 pet green anoles to which I feed common house crickets purchased from pet stores. I keep the crickets in a glass aquarium with some egg cartons to hide in, and shallow containers of Fluker’s Cricket Feed and Cricket Gel (a water substitute). I clean the tank once a week with a weak vinegar/water solution.

I have noticed that every time I get a batch of crickets, anywhere from a few to most of them end up dying within a few days. It seems that they always go through some kind of slow paralysis. I’ll see some struggling to run around with their back legs completely immobile, but the other legs are working. Then it progresses to where they are slowly moving their legs, but can’t go anywhere. In the end they lie there as if they are dead, but wiggle feebly when touched. Then they actually die. I know these crickets aren’t molting; I’ve seen many a molt before. Is this some kind of illness or nutritional deficit? Is there any way to prevent it? If I can keep them alive longer, I won’t have to buy them as often.