Help figuring out issue

[Scooby_Snacks]

Having an issue with my plant. Problem started about 1w - 1.5 week into flowering. This will be week 3. Strain I think is Blackberry.

Soil - organic mix from local M&P garden store.
Foxfarm nutes, full strength from soil feed guide, not bottle.
5 gal pail
temp tops out about 90.
ph of runoff and with testing meter is just under 7
nutes and feeding are ph'd to 6.6

I thought this was a Mg def, so I foliar fed and watered once with epson salt. I don't see any improvement after a few days. I'm now thinking it may be a Zn def but I'm not sure. I've had this issue before. It starts on the middle fan leaves and spreads upwards from there. Any help would be appreciated.

 

[Captain Kronic]

Looks like it could be an Iron def. also. When I think they need something, I will hit them w/Super Thrive, that's kind of my fix all when I don't know exactly what the problem is.
Best of all to ya M8!

 

[Droopy Dog]

Iron and Zinc def usually go together.

Iron and Mg def look the same, but iron affects the new growth first and Mg starts in the older leaves first.

That really looks like iron. Good thing is, most iron suppliments also contain zinc and Mn.

DD