Help, Leaf spotting.

What is your experience level? First Timer.

What type of hydro set-up are you running? DWC

Your Equipment:
A) Type and wattage of lights. 150 watt HPS & 65 watt 6500K CFL.
B) Distance from tops? 14"
C) Reflector type? Small standard reflector.
D) What are the bulb wattages, kelvin ratYings, and schedule? 150 HPS & 65 CFL 6500K. 20/4.
E) Is there a consistent fresh air supply? Yes.
F) Do you have an exhaust fan and a circulation fan? Yes & 4" circulating fan.
G) Size of reservoir? 4 Gal.
H) What medium if applicable. Hydocorn.

Your nutrients and water:
I) If using rockwoll for clones or seedlings, did you rinse the cubes well, with properly ph'd water? Yes.
J) Source of water. Tap. What's it's ph? 5.8-6.5.
K) Specific brand and N-P-K ratio for each bottle. List dosages (quantity per gallon) and current feeding schedule. Advance Sensi Grow 2 part, very light dose (7 mil to 4 gal) Started 7 days ago, plants are 18 days old now.
L) What is the ec/ppm of your unadjusted tap (or filtered) water? 55.
M) What is the ec/ppm of your nutrient solution? 200.
N) What is the temperature of your nutrient solution? 74-78.
O) Does your ec/ppm show a rise or fall when you do your daily PPM check? No.
P) Does the ph fluctuate? Yes.
Q) Do you foliar feed? No.
R) How often do you replace reservoir water/nutes? Havent yet. What does it look like before changes? Just a slight bit cloudy.

Your growroom:
S) What size of closet, room or hut? 2.5x2x5.
T) What are the temps and humidity levels while lights are on? 78-85, 38-55%. With lights off? 74, 45-60%.
U) Have you seen signs of insects in the growroom? Seen a couple small gnats.
V) Are the roots long and white, or brown and slimy? Long & white.

Your strain:
W) What strain are you growing? Sativa.
X) From seeds or clones? Seeds.
Y) Is this an autoflower strain? Yes.

My first set of leafs started spotting & curling about 5 days ago on one plant & now im seeing some very small spots on a couple of my other plant leafs. Any help is greatly appreciated. Thanks in advance!