Zinc or Iron ?

I believe some of my plants are having a zinc or iron deficiency? Can anyone tell which one? I'll check my ph again but it usually stays around 6.8, so what else can cause this? (Just saw last night that I have gnats as well, can they cause this or are they unrelated?) In both of these pics you can see some of the plants that appear to have stripes - it isn't the camera, they really look that way.

Boneman said:

If you've narrowed it down to those two, I would say Iron. Its hard to tell with the pics though.

Click to expand...

I'm kinda guessing based on the diagnosis guides - the plants don't show any sign of a problem, aside from the wierd stripes.

Boneman said:

I cant really tell from those pics but with a zinc def, the outer edges turn yellowish with the middle being green. Can it be nitrogen?

Click to expand...

The outer edges are not yellow. I don't know about Nitrogen, they are getting nutes, with a value of 12-4-8, as well as Superthrive at a drop per gallon, and one TBSP molassas per gallon of water. What do you think?

I just had a thought, some of the plants got quite a bit of plaster on them when we hung the lights, and probably been watered into the soil since - could this maybe be causing the problem?