Iron Deficiency or Something Else?

Hi. 2 of my friend's plants are showing some discoloration. The first looks almost exactly like iron deficiency (first 3 pictures), with the interveinal chlorosis starting at the youngest leaves and beginning to affect the lower, older ones. The second plant (last 2 pictures), though, I'm stumped. The way my friend initially described it made it sound like it was some kind of infectious agent spreading, because he noted that the two effected plants sit beside each other in the tray, but given that the first problem looks so much like iron deficiency I'm starting to think that both problems might be deficiencies (with the second being maybe Zinc?) causes by overly alkaline medium/water pH... unfortunately, I don't have any pH numbers from my fiend atm, will update with those as soon as I get them.

In terms of nutrients, plants are on veg nutes and haven't been fed in about 7 days.

Does appear ro be a nute deficiency. What kind of soil?
You might try Miracid. You can pick it up at any hardware and its cheap. It has a lot of the micronutrients that are missing in a lot of soils and nutes. I use 1 tspn per gallon once a week and it greens them right up.

It's in Promix BX.

That's a deficiency alright. Could be zinc or iron or sulphur or magnesium. Try a decent fertilizer with all the micro nutes or an additive. Just don't give too much of it.