[Absolem]

Originally Posted by searchingforit

Do you think 6/9 without the 1g of epsom is best? mg and S seem a tad low without it but it is also a 3:1 ca/mg ratio with no epsom added.

Check this post out.

https://www.icmag.com/ic/showthread.php?t=348058

[TanzanianMagic]

Originally Posted by searchingforit

Not all plants are showing this but a few are. They are under LED. Fed 6/9 + 1g epsom salt twice a day as they are in small pots. I have been chasing this deficiency since they were smaller. I tried scaling feeding back on the problem plants from 1.2 EC to .9 and worked up - same problem. Dark veins, interveinal chlorosis then these brown edges form with downward hooking. Growth is not right. Temps @ 80, RH 65%. RO mixed with tap for stability pHed to 5.8. Roots look great.

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It looks like a combo of N and K deficiency in early flowering. However, most likely this is because N and K what the plants are needing the most of right now, so that's how a lockout shows up and looks.

Gently flush the plants with 0.2 EC of high P/K late flowering solution, or just flowering solution.

You could also have a lack of magnesium, because of the R/O water. You can take a pinch of magnesium lime to a quart of water, let it stand for a day or so, and mix it with R/O water at 1:3 parts. That adds enough magnesium and calcium back to the water for ordinary feeding. In flower, weed needs extra magnesium, to keep the plant green and the leaves phototropic.

For watering/feeding, the most important thing is that it sits in a container next to the plants for at least an hour before use - you massively reduce watering/feeding shock by eliminating the difference in temperature between the nutrients and the pots.

[searchingforit]

These plants are not in flower. My rez is at a stable temp. I've been feeding 6/9 at full strength with .5 g epsom multiple times a day. The plants that were fine remain lush green while the problem plants look like trash. New growth remains good. I do think this is a K def.

Absolem, that is fantastic. I will have a look. Thank you.

[TanzanianMagic]

Originally Posted by searchingforit

These plants are not in flower. My rez is at a stable temp. I've been feeding 6/9 at full strength with .5 g epsom multiple times a day. The plants that were fine remain lush green while the problem plants look like trash. New growth remains good. I do think this is a K def.

I'll bet they already have quite a few pre-flowers. Increased need for phosphorus and magnesium starts that early. And considering you're using R/O water, that has the magnesium and calcium taken out of it...

[TanzanianMagic]

Just taking a second look at the 3rd picture. There are pre-flowers breaking out all over the plant.

I think the first concern should be magnesium. It could all be a magnesium deficiency because of combined effect of R/O water and pre-flowering/early flowering, which increases the need for magnesium, as well as phosphorus.