Looking for some input/help; my tank is suffering a big GHA & Cyano issue

[gregzz4]

I’ve been battling GHA since July 2014
I treated for Cyano last year
All was good until I messed with things …

I’d read about having balanced PO4 and NO3, and my NO3 was zero
Sometime back in Spring I tried to raise my NO3, as my corals were looking a bit lackluster. Note to self; don’t screw with the balance
Stupid me, I tried to raise my NO3 by feeding more. I know, you can’t raise NO3 by feedings … Lesson learned

I run Carbon and GFO
I change each monthly on a staggered schedule
Since this has happened, I've been changing the GFO weekly

The extra feedings didn’t go well. I’ve since had this ongoing issue with GHA, and it now turns out that what’s been killing all my snails is Cyano hiding in the algae
And on top of things I have to remove dead snails to stop the cycle (some poor buggers were brand new)

I’ve been changing my GFO weekly @ 150mls (instead of 225mls/month)
I’ve cut back the fishies daily pellets from 3 to 2 feedings for lunch, and just tonight cut it back again. They will only get one dose of pellets for now
They get one cube of frozen/night. It’s my mix that’s all rinsed and vitie blended.
I can’t cut the cube at night due to non-pellet eaters, but I may consider cutting a cube in half

My PO4 @ last test with my Hanna Digital was 0.02
With their variance, this could be either 0.06 or 0.008

I’ve been using PhosBuster Pro and haven’t seen a change yet with the GHA
I’ll continue to use it while I’m plucking what I can

Tonight, after 3 days of the PhosBuster stuff, I did a 15% WC
Normally I do 10%/week

I’ve been removing the GHA in clumps, big clumps, and I’ve had to regularly scrub some of my zoas as they are being overwhelmed by slime/algae

I don’t want to do a system reset at this point as my tank is finally starting to mature and some of my SPS are looking happy
It’s just past the 2-year mark

I've been thinking about changing my lighting schedule to reflect a MH unit
Instead of having my bulbs transition all day, I'm thinking about having a full-on light schedule during the afternoon to reflect a MH setup, and have my other T5s tuned lower to compensate for the difference

Any input is greatly appreciated