For sure they can be stunted.
It's time to get your rays onto some better food then mysis. Like said break a carnivore up and stay away from massivore (since you have a scobina) as i is way to big for your rays to start on. Use a pair of scissors to cut up market shrimp to very small pieces and if they won't take the pellets or shrimp start feeding cut up canadian nightcrawlers for awhile and then start marinating the shrimp and pellets in a cup of cut up worms. Many people believe you have to starve your ray to get it to eat other things which is untrue, just start blending your food and it will happen.
It's time to get your rays onto some better food then mysis. Like said break a carnivore up and stay away from massivore (since you have a scobina) as i is way to big for your rays to start on. Use a pair of scissors to cut up market shrimp to very small pieces and if they won't take the pellets or shrimp start feeding cut up canadian nightcrawlers for awhile and then start marinating the shrimp and pellets in a cup of cut up worms. Many people believe you have to starve your ray to get it to eat other things which is untrue, just start blending your food and it will happen.