HELP! Interveinal chlorosis/yellowing on upper growth

[azorahai]

I'm noticing my photoperiod plants (each picture is a different plant) are beginning to show some slight interveinal chlorosis (yellowing between the veins of a leaf) at the upper/newer growth, which looks very much like a magnesium deficiency to me but it's not showing on the lower/older growth as one would expect from such a deficiency (or any other mobile nutrient deficiency). The first plant is bouncing back from being overfertilized (both were lightly flushed with pH'd water a few days ago until run-off was within the target 1000-1200 ppm), so perhaps this has something to do with that. That being said, the interveinal chlorosis wasn't apparent on any plant when the first one started burning at the tips and yellowing all around the older growth from being overfert. Any ideas?

Both are grown on a mix of peat moss, perlite and vermiculite, and watered/fertilized with a pH of around 6.0-6.5. Last run-off indicated a pH of 6.4 and 6.0, respectively. My 180W LED lights are about 25 inches from the top, and temperature is ranging between 25-30 ºC. I still don't have a humidity meter, but I suspect the humidity is high, which is something I'm working on fixing.

Edit: zinc deficiency also seems to show up as interveinal chlorosis (particularly at the upper/newer growth), but I'm pretty sure I'm feeding it more zinc than most other growers (around 1.5 ppm) and the pH seems to be within range for its absorption.

Edit²: just did a slurry test (topsoil) of the first plant and the pH registered around 6.1

[gbauto]

I always have lighter colored growth tips.
Never seems to be an indicator of issues.
Overall, they look happy.
What are you feeding them?

[azorahai]

This is the first time I'm seeing this discoloring pattern on my plants, and they've been through some light burn/bleaching and overfertilization. I'm currently feeding them a mix of 20-05-20 NPK, dolomite lime (Mg, Ca) and all the necessary micronutrients (Zn, Mn, Fe, B, Cu, Mo). I did some calculations using two different feeding schedules for General Hydroponics fertilizers and found out what is the recommended ppm range for each nutrient, and I'm feeding my plants more micronutrients than most growers (for good measure, it's still within the manufacturer's recommended dosage) and slightly more NPK because mine won't dissolve 100% in water. They've been loving it so far.

[dilvish]

seems more like light stress if its only the new growth at the top. check the distance your plants are from the lights, give them a good flush and wait a week and see what happens. with an NPK ratio of 20-05-20 I'm surprised they aren't nutrient burned. Adding more nutrients doesn't do much if the light is not full spectrum. Think of nutrients as vitamins and full spectrum light as food...like humans our bodies won't absorb more vitamins than we need and in some cases if we get too much of a certain vitamin it causes liver problems!

FYI when trying to get help the more pics the better and descriptions of PH testing, nutrient types and frequency as well as lighting type (LED/COB, HPS, fluorescent etc.) is very helpful. Type of soil and pots used as well as heat and humidty are also good tips to give when getting a diagnosis. You gave some but not all so in future......

[azorahai]

I've had issues with light bleaching before, and this is very different. Also, the newer growth at the bottom also has the same interveinal chlorosis as the newer growth at the top.
Regarding the 20-05-20 NPK (or 4-1-4 NPK if that makes it any better), I haven't had any issues with it, except when I first fertilized and didn't even know what I was doing and more recently when I neglected to measure the run-off for salt buildup and put one of my plants into a nutrient lockout. The proportion seems fine to me, particularly because it wasn't really meant to be dissolved in water and thus isn't as readily available to the plants as are hydroponic fertilizers. That being said, I'm already planning on getting another fertilizer that is more manageable than this one.

[dilvish]

unless you knw exactly what you are doing then the nutrients will fail....best to stick with what works of course. That ratio of NPK seems too high but if your plants aren't showing burn then who knows. You said in the initial post that this discoloration wasn't happening on the lower part, now you are saying it is...again I'd say light burn or something very wrong with the nutrients. Personally I would stay away from peat moss too as sometimes it can be full of chemicals the plant doesn't like.

Additionally you say the PH is around 6.0-6.5...that's a bit of a stretch considering the window is 6.0-7.0 typically for soil/coir grown plants. Maybe double check PH levels again

[azorahai]

I'm sure you're trying to help, but you're coming across as very condescending. The original post and the follow-up had all the information that you asked, including a summary of my research on the recommended nutrient concentrations, and now you're suggesting the pH is strange because it is... exactly what is widely recommended? The pH meter is checked regularly against two buffer solutions, and I also use pH strips to ensure the meter isn't giving me wrong numbers.
The chlorosis is showing up on the newer growth and not on the older growth. Also, this looks nothing like light bleaching/burn, particularly because I've had issues with the LED lights being too close to the canopy and I know how it looks from experience.

[azorahai]

Follow-up: the interveinal chlorosis doesn't appear to have worsen. I suspect it really is zinc deficiency, as it only started showing after I lightly flushed the pot and didn't feed again. Although the run-off (after the flush) measured around 1000-1200 ppm, perhaps only the most soluble nutrients were flushed out leaving behind only the least soluble. From experience, the micronutrient mix dissolves very easily, whereas the NPK takes a good while to dissolve in water. I'll try flushing it again until is registers a significantly low ppm, and then immediately feed it. I'll let you know how it turns out.