Yellow leaves, starting at tips (lots of pics)

This is an indoor grow, under a 150w HPS, I've been watering every 7 days for about 3-4 weeks at least (adding 1/4 to 1/2 strength nutrients every 2 weeks/waterings). The medium is potting soil, humus, and vermiculite. The older plant has been in 12/12 for 13 weeks and the younger plant has been in 12/12 for 7 weeks.

Ok, so from the research I've done, this looks to be a potassium and magnesium deficiency. At first, I thought it was normal, since this girl has been in 12/12 for 13 weeks now (and leaves generally turn yellow as they age), but the same thing is happening with my younger plant, only at a much higher speed.

I just realized that the nutrient solution I've been using is probably not correct: 04-14-08 I also have a little bottle of 10-10-10, which I should probably switch to.

I flushed each of them on tuesday night (two days ago) so hopefully they are on their way to getting better. On the last scheduled feeding, I skipped the older plant, which maybe explains the lesser effect of yellowing.

On their next watering, they will be due for nutrients, so I'd really appreciate any suggestions.


Here are pics from last week - how it all began (day 115 from seed, 85 in 12/12, and 72 since sex)


Here are pics from today: (day 125)


And here is the younger plant today, which is doing even worse (day 95 from sprout, 55 from 12/12 start, and 43 from sex):

I would probably stick with the 04-14-08. 10-10-10 might be too much N. I had a similar problem
and I gave 'em a shot of Earth Juice Meta-K and Microblast. Took a while, but it eventually cleared
up. Hope you get it sorted out.

what's your pH?

thats deffinatly fert burn.

flush

Ph is in the mid to high 6's, so that shouldnt be an issue. Plus, i let my water sit out for at least 2 days, so it should be balanced. I dont know the soil ph- my tester doesnt do shit

ok test you soil this way.

poor in water till it begins to drain. collect a cup of the drainage. test.

Cool, I'll check the soil pH on my next watering - in about 2-3 days.

Any advice on exactly what to do? Should I lay off the nutes for another cycle and just keep flushing?

keep the answers coming im having the exact same problem, except i using foxfarms nutes and soil ocean forest

The problem is not getting any better. Could it possibly be heat burn from the light? They have done fine at this distance, but maybe they get more sensitive with a litle nute burn?

you answered it yourself,...1/4 to 1/2 feeds every 2 weeks isnt enough food. letting water sit out has nothing to do with ph balancing. just gets rid of chlorine. if your ph meter reads the food and water it can read the medium. do like the other said and test the run off. and with very little food and the flushes it needs food in a bad way. full feeds dood, 1/4 is for a seedling not a full grown plant

I don't believe it is nute burn, because many leaves are not harmed on the tips, but the margins show signs of necrosis on some of the leaf margins and many tips are not burned or harmed at all. I think your diagnoses is correct. Before you add additional food, you really need to PH correct your soil. I suspect your soil is alkaline and maybe blocking nutes. If PH is acceptable, I'd step up feeding. If it was nute burn, everyone of your leaf tips would show it.

You may also consider upgrading your light. For 13 weeks of 12/12, that first plant doesn't look anywhere near ready....

Actually, now that I think back, the wholle plant seemed to get more light sensitive, starting to yellow at the upper most leaves on the cola, which were nearest to the light. Leaves below followed suit, and the leaves which were most preserved were the ones away from the light.

I checked the soil PH, which turned out to be right at 6.9 - - even after pouring thru some water that was acidic (I added vinegar). Is this PH too high? The water I'm using (from a filter is coming out completely neutral). The nutes that I"m using is bringing the water PH down quite a bit.

Is there a deficiency or over-nuting that makes a plant more light sensitive? the odd thing is that both plants started doing this at the same time, even though they area about 30 days apart in age.

if the run off pH was 6.9 then thats fine. its not enough food to only be feeding 1/4 to half every 2 weeks. should be a feed, water, feed, water so on. and way stronmger. you should be at full feed long ago