Live phyto for nutrient uptake?

My tank has recently (slowly over a week) developed a cyano problem... =/  I've been running skimmerless, but 24/7 carbon, for 2 years without problem.  About 2 weeks ago I decided to try and ASM skimmer i bought from erik just to see what it might pull out of my system.  I was impressed it didn't pull nearly as much as i thought it might now that it is "warmed up" but it is pulling some so i know its working.  The only other thing that has changed recently from my normal routine is that I haven't added any live phyto that i grow in about two weeks.  All tank params test just fine, except Ph was minorly higher than normal.

The symptoms are a cyano bloom in the main taink and my two fungia are much less "fleshy" than normal.  Everything else, zoos, LPS, softies all look great and are fully extended.  So the cyano makes me think i've got an excess nutrient problem...  so i stop feeding for 4 days and do a 20% water change everyday for 4... no luck, same symptoms and everything tests dead on as before except Ph is now spot on.

So the question is... could all the phyto i was adding have been uptaking more excess nutrients than the skimmer can pull out?  Since it is live it shouldn't be adding to the excess nutrients but could it have really been having that much of a positive effect?  Any other thoughts on my cyano/fungia problem would be appreciated as well!

-dwn

PC lighting setup hasn't changed in probably two months, bulbs aren't quite 6 months old but maybe due for a change sometime soon.  Photo period is roughly 11 hours total with an 9 hours full intensity 1 hour on each end for ramp up / down.

now that i think about it, a few golf ball sized pieces of rubble LR i tossed in the sump just a few days ago to eventually mount frags.  they are trivial compared to the amount of LR i've got in the system though and i've added 10x as much with no ill effects in the past.

no new LS or fish.  a new  blasto frag saturday from steve lopez (thanks steve!) that is fully open and looking great.

the flow trick is usually a good one, the odd thing is the cyano is growing the thickest directly under the return where there is the highest concentration of water flow =/

if the LR was dying off i would expect a nitrate/nitrite/ammonia/something spike at least which is why i'm confused!

thanks
-dwn

The lighting may be the cause... the time of your lighting(for ease of math)is... more than 10hrs per day for over 180 days= 1800 hrs. There's alot that can be related to the usage of those pc's(quality of ballast, lights, temp, etc). Most manufacturers recommend changing out your lighting every 6 months to a year depending on amount of time used each day. I hope it's that simple...

Jason