Interesting. As it could also be water parameters, dosing supplements (or not), temp swings...etc.etc. and not just a lighting issue.
The few SPS I have (easy care for types) are growing well under my LEDs. Don't ask me the names of them... I have no idea (I'm SPS Dumb). I've HEARD, some are tough to care for... but, fity2pounder is using LEDs over his tank (and he's got more SPS than I, as well as harder-to-keep types). Best to ask him how his growth is doing, as he's using THE SAME LEDs I'm using (custom coloration).