Each method is different and not necessarily related or correlated to the other. It just depends on what you're trying to do. You may want to take the time to research each method, see why it's done and then decide what to do. Good luck.
If it were me, in the future, work the Epsom salt into your reservoir vs. spraying it. See if they green up with the Epsom. I wouldn't do too much more at the moment; they aren't that far off. Good luck.
That's what I would deduce from what you've just posted; yes.
Do you generally run Epsom Salt or is this the first time using it? Can you provide full plant pictures under ambient light?
I have to agree with hotrodharley, you've got something off in your pH. Your plants are showing multiple deficiencies. If your soil is full of nutrients, once you dial in your pH, you'll know it. Good luck.
I'm guessing it's a bit more than variegation. If it were, it'd be on pretty much all your leaves (maybe it is?). If you look beyond the leaves you're posting about, you'll see other leaves in your pics showing deficiencies and / or pH issues. This is where I'd start. Good luck.
How big of an LED? Your plants look as though they're getting a little too much of it.
You're also showing multiple deficiencies along different plants which would cause me to first be sure of everyone's pH.
Good luck.
Some helpful advice...
Keep your coco moist all the time...your coco looks dry.
Your pH range should fall within 5.6-6.0, with 5.8 pH being the sweet spot. You'll need to adjust it accordingly.
Always feed the plant....don't use plain water.
Good luck
I wouldn't flower plants that look like that. You need to fix them first or the flowering stage will be a waste. If you have two plants receiving the same nutrients and they don't look like this, I'd look at the pH of the two in question and I'd comb them over for bugs.