IMO its more then enuf. besides his tank is 18 inch deep.
I kept a whole lotta corals under t5s alone for more then a year and they do very well. even higher light demanding corals like lps n even some clams.
for shallow tanks HO t5s are enough to sustain. if zoos are loosing colour or stretching if could be alot of other factors like WATER QUALITY, WATER TEMPTERATURE, PEST such as nudibranches or maybe like what reddivils said, whey are fighting for space.
do not under estimate the power of t5s on smaller tanks... muahaha
here's a pic of the tank tt im talking abt( hope js dun mind)...