possible Zn def, no help from technaflora or schultz / wtf

Sup guys,
having issues. Major downer. Thought i knew what i was doing, but obviously not.
Im using Technaflora's "recipe for success".
BC Grow, BC Boost, Thrive Alive B1, MagiCal, for Veg stage.




Nutrient info -> http://www.technaflora.com/products.php?product=11
Using tap water PH'd to 6.8-7.
80% Fox Farms Ocean Soil / 20% perlite.
1000w enclosed HPS, 18-20 inches from top of plants.

My older babies have all been turning yellow. Literally 80% of my modest field has turned yellow. It is not just top leaves, the whole plants are yellowing. The new kids are all green as can be, other than slight nute burn issues caused by me trying to find a solution for older plants.

Heres what I tried:

• First try was to stop all feeding and water for a week.
• Problem got worse so i tried a full dose of Technaflora BC Grow/Boost (for the nitrogen)
• All that got me was some nute burn, toasted leaves.
• Plants still turning yellow.
• Nitrogen def should yellow old leaves and leave new leaves green, so decided it was iron/zinc def.
• Put some nails in water and let them rust. Not iron def, more nute burn.

That leaves Zinc, pesky sonofabitch.
Here is a older plant beside a young one. Take a look to confirm.









Now the problem is, a Zn def should be fixed by any zinc being introduced. As you can see, BC Grow contains zinc but its not helping. I then switched to Schultz Liquid Plant Food 10-15-10 http://www.schultz.com/NR/exeres/53739960-95B7-4FDC-BD19-A78181668714.htm
Which contains twice as much Zn. but still not a quick fix.
Any of u heads got some ideas for me?
gettin depressed here.

Looks over watered. Maybe a Sulfur issue. Add a tsp. of Epsom salt per gallon of solution the next time the soil goes dry and water with a good amount of run off.

Another Reason Bigger Pots Win. 1 plant can out-yield 5 of thoes. But back to your Issues, Breaks my Heart to See. >.< Knock on Wood.. Uhh, Lemme go chk on my grls.

one of my original thoughts was overwatering. Im watering these suckers once every 24h. I tried once every 48h but when i went to water them again they had all drooped and shriveled up. kind of scared to leave them any longer than 24h. That time might have been a combination of the lack of water and the unusually high temp fluctuation that day.
Im going to give them 2 days without water and then try the epsom salt idea.
will report back in tomorrow night with an update.