I respectfully disagree.
OP is already feeding calmag and his leaves look very green. I suspect he is doing just fine on the magnesium and N. Through trial and error, heavy N and magnesium can lockout K.
Magnesium deficiency will be fading between the veins and I’m not seeing any of that. This is 100% K deficiency. Not magnesium.
OP, do not feed extra magnesium.
Your right on your mag def discription I’m aware of that visual too
My discription is also true
How mag def shows
Depends on strain and or pheno
K is burnt serations starting at very tips of serations and workin in over time
Again, respectfully, I’m trying to help OP and his plant. Not argue about this. Magnesium is not his issue.
I also don’t know all the details about OP’s grow such as feed, environment, etc, but this plant needs potassium.
Giving more magnesium is going to hurt OP’s plant. Not fix it. This is the last post I’m making in this thread.
In the spirit of helpin the op
Whaley mackerel is 3/1/0
So zero k in feed lol
Pity that @Calcium_Enriched1996 isnt around for the glory
I also respectfully disagree with my friend, could be Potassium upon this comparation, here’s OP plant:
And here an example of K def:
Normally Magnesium has intervenial chlorosis and dark spots like this:
But those reddish zoned could also be Phosphorus (is there purple petioles?)
I think too much Calmag may have blocked Potassium or either Phosphorus:
I would flush and check runoff to have more data, could be experimenting a nutrient lockout … 
I don’t think anything is blocking p and k
There’s just very little in feed ( 3/1/0 )
: )
Yup, his nickname reminds me the Calcium conspiracy “Too much Calcium blocks Boron” 
and people abusing CalMag, miss that guy … 
lol Sorry if I was a bit short. I’ve just made some weird soil mixes in the past and looking at that plant gave me deja vu
I think I’ve read posts from that guy when googling random strains!
I’ve been experimenting with calcium in my soil mix lately and I tried to make an “AOL” style username. When I was K deficient I over-reacted and ended up with a bunch of stretchy plants covered in bugs. That’s why I didn’t choose “Potassium_Enriched”
Glad to see you back, we need experts here and we just have a good time throwing opinions, always learning from mistakes, I will have mackerel for dinner … 
Hardly consider myself an expert, just another guy making lots of mistakes and trying to learn from them!
Just to be clear here…pretty sure you referenced my picture as OP’s. So the debate here is only so relevant, but that’s all I’ve got to say haha
And to clear things up about my picture, it was from a harsh iso spray that dried many leaves out followed by a few 5.6-5.8(usual is 6.4) feedings because of a nutrient dosing issue. A response to my harsh conditions rather than what I was feeding it, if you get me. Anyway, keep on 
Ooooops, I shouldn’t reply to these threads from my mobile 
, thanks for clearing it out …
In the end it’s all about @Matt308 and his happiness
Now he can sleep sound tonite with a solid plan for the morning
: )
I won’t guess but Here’s some advice.
Stop using Fox Farm, it’s trash in a fancy bag. Will get you though veg easy enough but needs lots of amendments for flower. I know this from lots of experience .
And, get better with watering. It’s an underrated skill for us soil growers. Keeping the soil moist but not drenched and never dried out is important. Watering 5-10% of the pots volume is key to keeping up with your plants respiration and photosynthesis.
Good luck
That’s where i struggle in soil i think. Definitely over water. Then it gets to dry cause i think I’m drowning it.
