Also, what's the best way to utilize silica?
I personally like General hydroponics Armor Si. 1/2 strength, mainly because its so alkaline.
or use it as a PH adjuster.
However there are other ways. (untested by me tho')
-You could could make a aquaeous solution.
-Or use silica sand
Back in the day when I used to run 400's I would get lightburn around 4-6 inches,
With silica supplementation, running 1kw HPS, I start to see light bleaching & stress around 12-18 inches. Im starting to get a few too many growth points, so around 24 inches is where it seems to be the best.
I'm not saying its going to solve your problems, but it does what it says it does. I run my setups around 50WPSF, kinda high, I know.. but I like it like that.