a little late reply I know but,
in response to your question, I know Prime does several things AquaSafe doesn't,
changes things in thew water, adds things, takes out extra things... so it made have changed one of his levels, PH, etc.
since I can't remember the rest let's use PH as the example;
so if it changed the PH, it's really a lot like water temp change, if you just exposed him right to it, instead of getting him used to it, then just like sudden water temp change it might have freaked him and his system.... that's why a lot of people like to use the drip method to acclimate their fish rather than just floating, this gets them used to temperature AND allows them to ajust to whatever the new water may be like compared to their old water.
and as they said you might also break up the four pellets to two in morning and two at night, don't forget their stomachs are the size of their eye or smaller, that's a lot to cram in all at once. ^-^ breaking it up gives the first meal time to digest a little to make space for the second, but still gives him a good full daily feeding ^-^
one day of fasting a week never hurt either. makes mine cranky x3 but is good for him in the long run ^-^ hope he's doing well :D