Brown spots and confusion!

[GreeeeenThumb]

Hello,
Wondering if anyone can pls help with my brown spots that have spread to 3/4 of my plant?? The strain is Barney's Blue Cheese in a 20 gal pot with promix hp. Added a lil miracle grow in second week of July, started getting lil brown spots on leaves and it has spread since than. Tried adding a lil tomato higher potassium fertilizer a week ago and a lil lime. Seems to be getting worse! Just did a flush a couple days ago. Does it look like cal/mag deficiency??? Pls help

 

[beez0404]

See if this helps. It's a pretty thorough chart.

My opinion (and this is just my opinion don't take it as gospel) is that you have a magnesium deficiency. Looks like the plant is outside, is that where you're growing it?