Starve the little guys until they're hungry. Flowerhorns are pigs. When they are hungry they will eat. I just went through that with one of mine. My wife got it hooked on eating nightcrawlers.... and for around 2-3 weeks that's all he wanted to eat. So eventually I cut him back on feedings and gave him pellets once a day. Hes eating good on his original diet 2-3 time a day now. You're not going to hurt those fish if they go a couple days without eating