Need help w/ plant problem

High all,
The older fans leaves of several strains of my grow (Vanilla Kush, Orange Bud, and the Ultimate) have developed a problem that I can't seem to diagnose. I've included some pics below. I'm using an aero grow system ala StinkBud with Botanicare nutrients, ro water for the rez w/ nutes at about 1680 ppm. The 4 pics that show large portions of the leaves all seem to have the same symptoms, and the pic just showing the leaf tips is on a Skunk #11. That one doesn't have the problem shown in the first pics, but the older leaf tips are white or dead and curl down. Can anyone help me figure out what the problem(s) is?
Thanks again,
Robert in Arizona

whats the pH

could be mag/zinc deficiency also

There are signs of what could be Mg deficiency and maybe Phosphorus deficiency. The damage on a couple leaf blade edges is common with K def as well. Give them a properly pH'd fertilizer mix, focusing on Mg & P with some of everything else.

Hi again,
Sorry I didn't give a full description of the set up. The ph is 5.8, and the nutrients are mixed at 125 ml of Cal-Mag Plus, 180 ml of Liquid Karma, and 540 Pure Blend Pro Grow. This is exactly the ratio of ingredients that Botanicare suggests. Also, the 3 pics in the middle show up as being a white/yellow color, but that is just a result of the fact that my camera can't adjust for the light I'm using. In real life all the plants look generally healthy and green, and the new growth looks ok. But what I can't figure out is that, since this problem has exhibited itself through several rez changes, and since it has affected more than one strain, I pretty much have to be doing something wrong. I ppm level that starts to burn the plants is around 1780, so at 1680 they should be getting enough of everything they need, I would think. The room temp is around 75 and the rez temp is around 68. They are on an 18/6 light schedule. The genetics are Barney's Farm for the Vanilla Kush and Dutch Passion for the others. What am I forgetting????????????
Thanks again, Robert

I would think if its only happening on some strains, while others are fine, that your mix may be too strong for those strains. Skunk eats more or as much as any other strains I have tried, so I wouldn't use that as a baseline. I would experiment in backing off that ppm a little for the strains that are showing stress.

Thanks, Citrus, for your input, but the Skunk has shown the same problem, just not to the extent of the others. In fact, they have all pretty much shown the same thing to varying degrees, and over the last month I have removed some fan leaves that were way worse than those in the pics. Still perplexed.
Thanks again, Robert