Dial your pH (runoff) to about 6.5, add some cal/mag, and give her a couple days... Color may not fully return to damaged leaves, but it won't spread anymore... Looks like a shot of grow nutes might do her some good too... But again, could be pH and not a deficiency at all! I'd check and adjust your pH and allow a couple days to start soaking up some mag; I'd probably do a flush to make sure it's not a build up of insoluble salts (happens with pH low or high) most certainly not recieveing magnesium, note the fading color from center to edge, and worse from bottom to top... pH first, flush for salts, add cal/mag if needed... Hope this helps!