Autoflower Problems (WW, Afgan, Blueberry) Under-Nuted?

I have 3 autoflower strains starting on their 5th week. Blueberry, White Widow, and Afgan Kush.

Style: DWC
Light: 400w HPS @ 3 feet above plants on an 18/6 cycle
Air Temp: 75-81F
Water temp: 67-72F
PH: 5.8-6.1 - General Hydroponics PH Down
Nutrients: CNS17 Bloom - 8 ml/g
CNS17 Grow - 2 ml/g
Advanced Floriculture Cal-Mag - 1 ml/g
Rhizotonic 4.5 ml/g
PPM: 575
Air Stones: 2-18'' wands
Water Circulation: 20/gal/hr pump
Water Tank: 20/g reservoir with 14/g of water (constant water level)

Over the past week we have developed spots on the leaves of the afgan, then started on the whitewidow and has lightly started on the blueberry. I'm under the assumption that I am under-nuted or have a calcium deficiency because of the color and size of the spots that have developed on the fan leaves (ONLY OLD GROWTH, new growth is fine). I bought the Cal-Mag I put 1/ml/gal in (1/3 recommended dose)

Should I add more bloom?
Or do I have another problem?
Any input is greatly appreciated!

(I'll add better pictures when the light is about to shut off)

Ive had similar issues... about the same as yours. Not a biggie. Let the Cal/Mag run its course... may take a couple of weeks but that is what it looks like. You nutes are a bit low... but Ive never grown an autoflower strain. My girls in the bloom room are usually around 1200 ppm. You can also try some Cornucopia Plus. Its a really good natural booster. Plants love it. http://www.gtghydroponics.com/store/0-0-761.htm

Good luck.