Tiger Striping Fan Leaves During Flowering?

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I'm growing Humboldt Seed Organisation's Blue Dream...

I'm growing two plants, each in their own 14 gallon DWC equipped with two air stones each. I'm following the labels on the Gen. Hydroponics Flora series nutes. I vegged under 600w MH and am currently flowering in a 4'x4' ScROG under a single 600w air-cooled HPS.

The pics above illustrate my concern. I'm seeing some yellowing happening in that sort of tiger striped fashion. I thought maybe it was heat stress... I moved the light up a few inches more... Nothing changed after two days. My second thought was nute lockout... but when I check ph it's anywhere between 5.6 and 5.9. I try to keep it right at 5.8. PPM stays roughly the same or even drops a little with the water uptake (1/2 gallon per plant per day).

So here I am asking you what you think it might be. I don't want to treat the wrong problem. I'm 20+ days into flowering and everything else seems to be going well. I should also point out that the yellowing is happening around the tops of the plants... And closer to the middle of the screen. I can't tell yet, but it feels like the yellow is spreading outward towards the edges of the canopy.

Any help is appreciated. More info about my grow here:

https://www.rollitup.org/grow-journals/705725-first-grow-ever-hso-blue.html

Thanks in advance!

Magnesium deficiency are: space between the
veins (Interveinal) of older leaves; may begin around interior perimeter of leaf.
Problems with Magnesium being locked out by PH troubles
Light Acid Soils, soils with excessive potassium, calcium and or phosphorus
Soil
Magnesium gets locked out of soil growing at pH levels of 2.0-6.4
Magnesium is absorbed best in soil at a pH level of 6.5-9.1 . (I wouldn’t
recommend having a pH of over 7.0 in soil) anything out of the ranges listed will
contribute to a Magnesium deficiency.
Hydro and Soil less Mediums
Magnesium gets locked out of Hydro and Soil less Mediums at pH levels of 2.0-
5.7. Magnesium is absorbed best in Hydro and Soil less Mediums at pH levels of
5.8-9.1
(I wouldn’t recommend having a pH over 6.5 in hydro and soil less mediums.)
Best range for hydro and soil less mediums is 5.0 to 6.0. Anything out of the
ranges listed will contribute to a Magnesium deficiency.
Solution for Fixing a Magnesium Deficiency
Any Chemical/Organic nutrients that have Magnesium in them will fix a
Magnesium deficiency. (Only mixing at ½ strength when using chemical nutrients
or it will cause nutrient burn!)
Other nutrients that have magnesium in them are: Epsom salts, which is fast
absorption. Dolomite lime and or garden lime (same thing just called different)
which is slow absorption. Sulfate of Potash, Magnesia which is medium
absorption. Worm Castings, which is slow absorption. Crabshell which is slow
absorption. Earth Juice Mircoblast, which is fast acting. (a must buy!! Has lots of
2ndary nutrients).
Now if you added to much chemical nutrients and or organics, (which is hard to
burn your plants when using organics) You need to Flush the soil with plain
water. You need to use 2 times as much water as the size of the pot, for
example: If you have a 5 gallon pot and need to flush it, you need to use 10
gallons of water to rinse out the soil good enough to get rid of excessive
nutrients.

its a copy and paste mess. thats what i think is up with your plants. its quite common. check out other people with mag issues using the search tool to see for yourself.

I think you've been outdone.....Now that's a copy and paste mess...^^^

Edit: Aw the random spam message got deleted...now my comment makes no sense

So it's a mag deficiency?

IMO- Pic1-Phosphorus deficiency, Pic2-Magnesium deficiency.

Just a side note: When u increase nutrients do so very little at a time. You don't want to bump too much and burn em like I did by mistake in week 4 of flower. livin n learning to grow another the hard way!