Make sure the calcium levels stay high. Before I started checking my Ca levels, they dropped really low. I was feeding my candycanes and they wanted to grow, but could not build skeleton fast enough. They ended up looking like a giant brain coral with several mouths on one stalk. Soon the flesh became so heavy that it burst open. pieces of flesh hit the bottom of the tank and started making new heads of coral. Now I have lots of little baby candycane all over my substrate. Now I test my calcium, and dose kalkwasser to keep it high. My LPS are growing much better now.
To answer your question, only feed as much as they will willingly take. If they drop the food, they are not hungry. Only feed once or twice a week, or your phosphates will skyrocket (that is what happened to me too).
dsoz