I use a variety off food, cichlid colour pellets, cichlid omni flakes, yetra colour flakes, frozen cichlid mix and occasionally peas and cucumberDo larger ones. I do 2 70% changes a week. But some fish are very slow growers. No matter what you do, you can't change that. But better water conditions and good nutrition, you they will grow as fast as they can.
What foods are you offering? Diet requirements really vary between species.