Do I have an (Mg) issue?

Last resort , if you are brave and smart, wait till she dries out, transplant her into 3 times bigger house ( not less ) with fresh soil. Water her. No feeding for 3 weeks and she should recover. So only plain, phed water when needed !!! Not everyone will agree, but it works in soil with big screw ups.

You overfed, but i think ph its off too. You had clawing up 15 days ago in previous question. Plain phed to 6.3 dechlorinated water with 10% aprox run off. Water slowly, let soil saturate well. But wet/dry cycle is must. Lift pots, water only dry one, never rush to water. Throw out that nute line and egg shells. Be serious. Stop playing. Small wise investment into food. Go simple, something like TNC CalMag and FoxFarm trio, or 3 main from Biobizz. If have extra cash - Great White mycorrhizae. Feed half of recomended, dont start feeding for first 3 full weeks. Do feed/plain/feed/plain regime. So in reality you will use quater of recomended. Growing is easy if you have plan and dont overdo things. Have fun !

Plant is in lockout, check ph. Heavy flush and load right if coco If soil you are screwed , but can try to bring them back to finish. No flush in soil. Good watering regime and right diet.

pic #3 is an optical illusion due to grow lights, i think... the swollen interveinal areas i bet are a solid green color despite what teh pictures show? look in normal light if you can. the paling tip in from bottom up is probablay nitrogen related. as it progresses you do get those necrotic spots later on too. Pic #4 definitely shows some interveinal and dead spots, which could be Mg-def related. As others said, pH and concentration of other nutes can all impact availability, even if it is physicall present. Eliminate that stuff, then flip a coin as to how you wantn to attack it.. take notes; see what happens. Learn a bit to make the next time easier. Don't do 1 thing, flip-flop and do a different thing before you see the actual impact of the change. it'll be better for your learning curve in the long-run if you do. When you run around like a chicken with its head cutoff it's hard to figure out what was done that actually worked.

Are you keeping your pH in check?

Have a look at some pictures of potassium deficiency phosphorus deficiency and magnesium deficiency. Compare the pictures to your leaves, to me it looks like it could have a bit of all 3 of the above. If it is that then check your using the right NPK formula for flower and your in the correct PH range for your growing medium. As I'm the 1st to answer don't just close the question wait for a few more replies. It's better to have a few opinions then just one.