black spot, shadow

[Rusty Trichome]

Your Equipment:
.1) Type and wattage of lights - 600 HPS
.2) Distance from tops? 12inch
.3) Reflector type? (cool tube set-up)

Figured it must be a cool tube. What's your current lighting schedule?

Your nutrients and water:
10) Source of water? tap, What's it's ph before adjusting? ph9
11) Method of checking water ph. (GHE concentrate test indicator)
12) Method of adjusting water ph. (PH down)

Ouch. Mine's 8.0 ph out of the tap, I use phDown too. What ph are you adjusting the water to?

13) Specific brand and N-P-K ratio for each bottle. plagron alga-grow 4ml/1L
14) How often are you watering between feedings, and how much per watering? every 2 days, 400ml

Is this the stuff...?: Plagron Alga-Grow - £6.95 : Gavsgrow, Organic and Hydroponic Garden Supplies
Usage: Dilute 1-2 ml with 1 litre of water. Water the plants with this dilution once a week.
N:P:K - 4.0:6.0:8.0 - A flowering formula. Sort of. Shitloads of potassium, possibly screwing with your ph.

15) Any additives or tea's? (not yet)

A little info about teas: Compost tea myths...