I am not too up on my T5HO stats but from what I have learned, I do not think 3 bulbs will give you enough penetration on a 56 gal
cube tank. At 24" deap (?), you would actually do better with up to 6 bulbs.
Anemones will move for a variety of reasons but the two greatest are light and water flow. If they are not optimum, the anemone will wander trying to find the right conditions. Water flow should generally be about medium and for the two you have lighting should be on the higher side.
I would love to see the tank with the lights, so a pic would be great
. If not, how high is the rock? I would suggest building it up so the anemones can get closer to the light. Just be sure it is not in the dierct path of a water jet.