It's a simple matter that they've been spoiled, like a kid who gets candy and ice cream all the time and won't eat real food. Cyphoilapia can go a long time without eating and some get really stubborn about food. They may need to get good and hungry first.
If it was me I wouldn't feed every day, I'd go two three days and without feeding at all, let them learn food is not so readily available. Then introduce something dry, could be but doesn't have to be pellets just yet, could be freeze dried shrimps, mysis is good for growth. Then don't overfeed trying to make up for lost time, feed just a little or a moderate amount, not enough for them to be satisfied. Then wait at least another day or two, don't feed again the next day. Teaches them to feed when food's available.
Lot of people don't feed Cyphotilapia every day, anyway. Some feed only 2-3 times a week. You can feed more often in smallish or moderate amounts, but Cyphotilapia are not a high energy use fish and don't need as much food per their size as some other types.