You need to feed more often with a better variety of food, I would take him back, Blue rams should be kept in waters with a temperature of 28-32oC with a PH of 5-6.6 and a GH of 0-12, fail to meet these and they won't last two seconds.
In the meantime, feed him blood worms once weekly, and brine shrimp every few days, along with flakes, Also you can try tuna.