Need help with WW

So we have done Hydro and never had a problem but we started three WW clones and can't seem to get it right. It looks like mag deficiency ? But not sure. Ph was running high and used ph down two days ago and it is at 6 now. Took off bad leaves but now have more. Only one has rooted through the net pots. Ppm is 740 which I think is too high. Res temp is 68. The only thing I did different was used Aqua shield which I thought would help? I can't do a complete res change until this weekend. I do have sledgehammer, would adding that help or do I have to do that with clean res?

I just went through a mag deficiency and it effected the lower growth while the new growth looked good. The lowest leaves actually turned pale yellow with brown blotches. Try a weak foiler feed of epsom salts and if indeed a mag problem it will be better in a couple of days. And yes ppm's may be a tad high.

I dumpers ten gallons and added fresh. Ppm is now at 450 will give them a couple days and if no improvement I will try a foliage. Thanks

Plants at that stage should never have pH above 5.6-5.8

improper ph will lock out the nutrients in hydro. so even if you push the ppm to 50000000 nutrients the ph is to high the plant cant absorb or use the nutrients . it will look like its starving . so start over get the ph about 5.5 and redo your nutrients , and check the ph after you add the nutrients . because the plant does look like it is starving . also keep your water temps under control .

I missed your PH levels opps. But as SS says try a bit lower as well.