Plants are dying

First off, this is my first post, so hello everyone! And this is a legal grow, I'm a medical patient!

Now some details
Grow medium : Coco Coir, with about 30% perlite and verm
Age : started in late January
Strain : the one that's closest to dying is California orange, and the other is gorilla ice cream.

Also you can see the Cali orange has a tilted stem, I had started LST before this issue started. I didn't break the stem or anything.

I've spent hours on forums, and after a lot of research, I assumed it was a PH lockout. However I flushed really well, for the next several waterings, and the PH runoff was perfect. I keep ph in the 5.8-6.5 range.
I've had a nasty fungus gnat problem that I thought I had solved with neem oil, but they came back with a vengeance, so I started using diatomaceous earth on the top of the coir, along w trying the pots out as much as possible because I read that helps. I have another plant that's flowering so I can't continue the neem oil (don't wanna mess with the smell and taste of buds).
Is it possible that these plants are dying because of a severe fungus gnat infestation? I've tried everything to get rid of them, and if y'all suspect it's root damage from the gnats, I'll go ahead and invest in some heavy duty gnat killer.

Oh yeah, after about 2 weeks of flushing it with plain water, I gave it some more nutrients (5-4-2 biolive with active microbes and fungus and shit for the soil, mixed with a little dose of blood meal for extra N in case of a N deficiency ) and it doesn't seem to care. It's still slowly dying.

So this last watering, I gave it a dose of water with Epsom salts, because I figured it could be a MG deficiency. And read that it'll perk up within a few hours if it is. No luck.


Anyways sorry for the essay, any help would be greatly appreciated.

Observations, in terms of growing in coco:

1. Grow medium : Coco Coir, with about 30% perlite and verm ......Don't use vermiculite in the future; it holds water, and that is not what you want.
2. I keep ph in the 5.8-6.5 range.... Your range should be from @ 5.6 to 6.1, with 5.8 being the sweet spot; a pH of 6.5 is way too high for a coco grow.
3. along w trying the pots out as much as possible....I'm assuming you meant drying ('trying): you never want a coco plant to dry out....gnats or not.
4. 2 weeks of flushing it with plain water...you should never water a coco grow with plain water.

These 4 things alone are not helping you be successful. I would research the idiosyncrasies of growing in coco, before going much further; you'll be more successful. Good luck friend.