Is this a magnesium problem?

[pkands]

This shot is of a 5 week old northern light auto leaf.
Are the blotchy areas an early magnesium deficiency?

 

[Waira]

...Hmmm, too soon to say, with such early symptoms,.. there is some overlap with interveinal chlorosis with other defc.'s... is it from a lower fan? are you using a Ca-Mg supplement?

 

[pkands]

It is a lower fan leaf but whatever this is seems to be in all the leaves once they are big enough to see it.
I haven't used a Ca-Mg supplement but intend to get one Monday.
I'm using "crazy good dirt" and have used dilute fox farm products a couple of times only.
This is my first grow and whatever this is, is affecting all 5 plants.

 

[Waira]

Hmmm, could be a soil issue, possibly pH related, if all plants are showing this,... we need to determine if this is a lack-of defc., or a pH lockout issue meaning the nutes are there, but unavailable for absorption ....what's this soil deal, a custom blend, or hand made by yourself? can you tell me what's in it? Some whole plant pics would be helpful too,...