More frequent waterings in less quantities always helped for me in ffof. Lots of water keeps that soil acidic in the 4.5 -5 range which can lockout most nutrients. With ffof ph ur water to 6.8 or so. It will look like a deficiency and u will throw all kinds of stuff at it adding insult to injury. I wont use it anymore because its so hard to gauge when ur gonna burn ur plants when they are small, even at 1/4 strength nutes. Id try some light feeds now, begin with 1/4 strength and work ur way up to 1/2. Watch for leaf tip burn. If ur using RO or distilled water dont forget to get a cal-mag supplement.
I run coco loco now its awesome.ill be going straight coco next grow but didnt have many problems with that soil.