Magnesium Deficiency ????

I am growing Hydro, Pineapple Train Wreck. When in Veg they were Mag hogs and I was foliar feeding them. I am now a week into Flower and I am seeing symptoms of Mag Def, would appreciate any help. On the picture of the leaf, in between the serrated edges started out light green and now has turned a copper or bronze color. This is only on a few plants. Also on a few plants the very tip of the leaf points down.

Other than that my girls look great

Thanks

are the bottom of stems goin a purple colour on botton leaves

The particular leaves are fan leaves just under flower, the stem on the fan leaves are a purple tint, but no purple under the leaf.

The main stalk has lines of purple running up it, pin stripe effect

wats ur ppm at an ur ph

PPM 1200, using Cutting Edge Solutions they recommend 1400 to 1600, PH 5.5 to 6.5

It appears to me based on this guide, which I have read for days now, (Thanks for posting it) I have MG, K and CA, but which one is dominant. Funny how all three of these elements are together on the periodic table of elements

Cutting Edge has a mag and cal additive no? I think its called "Amp" or something along that line. Are you using that with your nutes?