Plants are dying on me, need some help / advice?

This is slowly progressing and getting worse. Spotting and dying has been creeping up from the bottom leaves, starting with black spots all over, to the outsides dying, to the leave crumbling off. I thought it was phosphorus but giving it nutrients every other watering is not helping. Giving them 3 teaspoons/ gal of floragro by general hydro, and 2 teaspoons/gal of florabloom and 1 tsp/gal of floramicro. It is slowly killing the plant and at this rate they only have a couple days left. Anything to be done?

SETUP:

• 400 watt HID, maybe will supplement with 150 watt hps soon.
• 6 inch inline fan and filter combo
• ProMix BX soil
• General Hydrobonics Florabloom Nutes
• Growing in a Secret Jardin Pro II DR120 and 6" Cooltube
• General Hydroponics Floragrow nutes.

Runoff PH is also at about 6.5, so 6.5 for water going in, 6.5 runoff. Confusing since thought it might be ph lockout. Any help would be greatly, greatly appreciated. Thanks all.

Are these autos? if they are you should not be feeding them that many nutes yet

No they aren't. I read that promix is a base soil that has next to no natural nutrients, is that true do you know? And I will flush the soil at their next watering then to try and get it out. What would be causing the dying then if the PH is within an acceptable range?

Check a drain water, ppm should be <500, if not - rinse the soil.

Simple soulution for next time go recycling system clay rocks for bigger better healthier crops and change to 600w lights It sounds like a root problem use something like bounce back stops wilting root rot and kills anything that could be harming them then check salt leaves and ph if that ain't it check for pests bugs some you carnt see so I suggest you go get a folar spray that kills any bugs or pests

what kind of water are you using.....I'm guessing Cal-Mag may help your situation

I would also back-off the nutes for awhile