That dark stuff on the leaf.

Your Equipment:
A) Type and wattage of lights. (MH, HPS, CFL's, tube fluorescents, LED's) 400w HPS
B) Distance from tops?
30cm
C) Reflector type? (cool tube set-up, bat wing, enclosed reflector, bare bulb...)
bat wing
D) What are the bulb wattages, kelvin ratings, and schedule?
400watt 18/6
E) Is there a consistent fresh air supply?
Yes
F) Do you have an exhaust fan and a circulation fan?
Yes
G) Size of reservoir?
30L
Your nutrients and water:
H) Source of water. (tap or filtered) What's it's ph?
Tap, 7.4 adjusted to 5.5-6.0
I) Specific brand and N-P-K ratio for each bottle. List dosages (quantity per gallon) and current feeding schedule.
Hydromino accelerant, 2 part, 5mins every 6 hours
J) What is the ec/ppm of your unadjusted tap (or filtered) water?
0.6
K) What is the ec/ppm of your nutrient solution?
1.9-2.1
L) What is the temperature of your nutrient solution? (reservoir high and low temps)
Dont know? 15c id say
M) Does your ec/ppm show a rise or fall when you do your daily PPM check?
Stays sameish
N) Does the ph fluctuate?
Goes UP
O) Do you foliar feed? If so, with what, how often, and at what time do you
spray? (Just after lights come on, just before they go out...)
Nah
P) How often do you replace reservoir water/nutes?
Weekly

Your growroom:
Q) What size of closet, room or hut?
1x1x2(small)
R) What are the temps and humidity levels while lights are on? ...With lights off?
20-24 degrees on, 16-18 off, 50% humid
S) Have you seen signs of insects in the growroom?
A few bugs near the light but not really., there is some algea on the perlite
T) Are the roots long and white, or brown and slimy?
Dont know