Have them under T5s, about 18 to 20 inches below the lights. My mushrooms do that too and I have them all over the tank, top and bottom. I bought my lighting system on ebay with no research. It was great for my fish but a friend gave me some shrooms and then I found the acans. It has 4 bulbs (2 - 10,000k coralife, and 2 actinic blue coralife bulbs. I even took 1 blue bulb out recently and replaced it with another 10,000k so Im running 3 and all of them are still stretched out like that.
I have been target feeding with frozen mysis shrimp and Coral Vibrance coral food (something my LFS advised me to try) and they are eating.
Do you think its my lighting?