STN in Acros, Now what to do?

[Bruce Leroy]

Have a 40 gal SPS Reef. all Acros/Milli's grew like mad, even spreading to rocks next to them.
Did a small water change after 4 months, everything was fine.
Changed out the HydroCarbon 3 days after water change,(Passive use) and all Acros started to STN Base up.
Fragged them all ,but still lost them .
All Monti's and Caps still look great and growing like mad.
Since STN episode, have changed out a few gallons every week for a month now.
Anything else I should be doing after this event?
TIA!
-Bruce

[eskymick]

You didn't mention any parameters, but I'd want to keep a close eye on alk levels.

[Bruce Leroy]

Alk: 7
Mag:1500
CAl: 400
S.G:1.025

[Paulairduck]

Did you increase the dosage of carbon? This can cause STN