i have had zoa's stretch under the same lighting i have run for years. I use a kessil a360 and had the 350 before that so Im on LEDs compared to your t5's, but I did as others suggested and moved it higher to get more light. That actually increased my stretching...I eventually moved them to the bottom of the tank in a "repair area" to keep them away from coral that was doing well, and this seemed to to get them to stop stretching. That being said after they normaled out for a few months they did eventually melt and die.
Lighting is definitely a good indicator of stretching zoa's but not always the case.
Okay I see I wanna do t5 / led set up but I don't really know much about led . I have a lot of high end zoas and I just don't wanna throw In some random led and mess everything up .