Not Mg def... we should all be able to recognize that by now: Mg def presents as REGULAR STRIPES between veins.

That's K def, textbook. You have it as a lockout coming from soggy, acidic soil conditions.

You are using pots with built-in drip trays I'll bet, and as a result, both drainage and the ability of oxygen to get at teh root zone are greatly impacted, resulting in soggy soil and reducing/anaerobic conditions. Ph is probably dropped out of range too by the looks of things.

Rip off the drip trays, drill additional holes in the sides of the pot, flush with pH'd water, water with a grow fert at 1/4 strength plus some Serenade if you have it (those conditions are perfect for fungus).