Magnesium deficiency?

Hi everyone, this is my first grow and I'm so upset with myself for not catching this sooner. Almost positive I have a magnesium deficiency and despite my best efforts, nothing has worked (flushing, giving cal mag). At this point, the one on the bottom right is ready to harvest (I think) and the bottom left isn't far behind. But the back left guy is not an auto, so I'm hoping I can save him. I ordered larger pots to move him into, if that's safe? I think they depleted the soil and I didn't supplement quickly enough. I'd love advice!!

You have more issues than that

Medium?
Nutes and amount of manufacturer suggested
pH
Etc etc etc

It escalated quickly. I have a mix of organic foxfarm ocean floor, foxfarm forest I think it is and 1/5 coco fiber. Only pH'd water for quite a few weeks (pH6.3-6.7) and then I started noticing the bottom leaves turning yellow, so I added 3T of cal-mag in 2 gallons of water. I really didn't add much of anything to the bottom two plants because they were great until about week 5/6 and at that point they already were starting to flower, so I just used organic bloom according to the bottle (I believe a capful in a gallon). I honestly didn't feed them much at all though, and only every other water, because I read that you don't need much added to good soil. I'm so bummed about this, I put so much time and energy, then they just got so bad so quickly

And this is the front right plant (Critical 2.0), which I think is ready for harvest, but I'm not sure. I added some cal mag and it started growing green leaves, but still looks like shit

This is the front (bottom) left one (GG auto).
They smell amazing, insanely sticky, especially the Critical, but I'm so worried that I totally fucked up my whole harvest. I already have a fraction of what I wanted as far as quality.

These are my Green Crack in the small tent, which I plan to move. Am I right to transplant these regular guys into larger pots? They're all in 3 gallon fabric pots. I can't get a better photo now, but they seem to be great, just like my others were. As soon as they started to flower, it all went to shit

This was July 12.
Got so bad so quickly