Growing in peat-based mediums requires an ingoing ph of between 6.3 and 6.8 ph. Higher or lower than that and you'll start to lock-out nutrients. (causing the leaf yellowing)

Check online for proper feeding ratio's with your Flora products, and follow the weekly schedule. (http://www.generalhydroponics.com/ge...-FeedChart.pdf

But yellowing with brownish-grey spots is a sign of overwatering. Feeding is most important, so only water inbetween feedings if the soil is almost completely dry.