Leaves are drying out near harvest

I have a bubble bucket plant and a soil plant in the same small grow tent and both are nearing harvest. Both are autos but different strains (white widow and northern lights).


They have grown fine without problems so far, but the leaves on the top colas and other top flowering stems of both plants have become dry/brittle and the edges are curved up a bit and the tips break when I bend them.
It affects both the fan leaves and the sugar leaves near the tops of the flower stems. The leaves a bit further down on the branches are still soft and silky.


The plants don't share the same nutes but they are in the same environment, so I am wondering whether the dry leaves are caused by heat, the fan or the natural progression of top leaves as the colas mature.


The tent has a 7 inch oscillating fan that sweeps across the tops of the plants. It sits about one foot away from the plants because the tent is not very large.
I have a 600W dual spectrum hid light in an air-cooled reflector and the light was about 10 inches above the tops ( I have since moved it up to about 16 inches above the tops).
The humidity and temps in the tent average 18-28C and 45-70% humidity.


Since it affects both plants, it should not be due to the nutes.
I suspect the light or the fan, but I wonder if this is also a natural part of the life cycle of the plants.


Also, should I just trim those dry leaves off and let the buds get a bit more light before harvest?
The plants have plenty of other leaves further down on the branches, and I notice that people often show photos of plants near harvest that look like they have been trimmed of most leaves on the flowering branches.


Any advice would be appreciated, as I don't want to screw up a decent grow right at the end. Thanks.

pictures would help a lot, tho a 3th option could be too little P/K in flowering (just a suggestion tho based on your pictures, try google it)

45-70% humidity is quite a lot of water in the air, being so close to harvest keep an eye out for mold problems. if its a small tent make sure the airs being exchanged properly. my air gets sucked out of the top and i have an inlet at the bottom with two fans. one at the base of the pots and one at the top like yours. what I've experienced with the top fan is if the fan leafs are hitting each other violently as the fan oscillates, eventually the leafs will get "wind hammered", i dunno if thats a correct term i just made that up. if thats the case, back the fan speed down a bit. It can also be that the plants are just naturally finishing out. Plants like these usually tend to cannibalize themselves to properly ripen. Also, i wouldnt pick half green leafs off the plants only the brown ones, if they are going to fall off let them naturally fall off. Post a picture of the plants if you can. it would be easier to help.

Thanks a lot.
This is a photo of some dry leaves around the tops of stems. A few inches lower, the leaves are soft and supple.

what day in flower or how close are you to harvest

look burned to me (to much nutrients/nitrogen) maybe a PH issue as well ?

It has been flowering for about 55 days. It is an auto that was planted on dec 1 and sprouted on dec 4 and showed the first pistils around dec 25. It was grown in a hydro bubble bucket.
I figure it needs about 2 more weeks. The trichs are milky and clear and the pistils are just beginning to darken.

Slipon said:

look burned to me (to much nutrients/nitrogen) maybe a PH issue as well ?

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Why only on the top leaves?
Leaves a few inches lower are all soft and supple.

when I have a PH issue or gave em to much nutrients (happens once) it did affect the new/top growth, when I have a defeiency and the plant lack some kind of nutrients/micros it show on the lower leaves first, dunno, guess it how the plant react

a sure sign of a PH that is out of track is curling leaves that curl up or down and look odd (like yours) nutrients burns do often show as burned leave tip/edges (brown tip`s) and from the picture don't look much like it ? but agin its hard to tell from one picture, keep reading/researching and take the advice you find most logic, in the end you learn to read your plant`s and after all there are only one person who can make the decision

if your this close to harvest i wouldnt want to change much. just keep it as simple as possible before u start your final flush

Slipon said:

when I have a PH issue or gave em to much nutrients (happens once) it did affect the new/top growth, when I have a defeiency and the plant lack some kind of nutrients/micros it show on the lower leaves first, dunno, guess it how the plant react

a sure sign of a PH that is out of track is curling leaves that curl up or down and look odd (like yours) nutrients burns do often show as burned leave tip/edges (brown tip`s) and from the picture don't look much like it ? but agin its hard to tell from one picture, keep reading/researching and take the advice you find most logic, in the end you learn to read your plant`s and after all there are only one person who can make the decision

Click to expand...

Thanks.
I do check the pH/ec/ppms every day and I have noticed a pattern that has developed in recent weeks.
I start the nutes at pH 5.4 and then it drifts up over the next 4 days to about 6.1 and then it starts drifting back down for a couple of days and then suddenlycrashing down to about 4.5 and I keep adjusting it back to 5.8-5.9 when I top up the bucket with regular pH 5.8 water every day.
Meanwhile, the ec and ppms drop gradually over the course of the week.

I have followed the canna aqua guide for nutes and my bubble bucket is 20L size and it holds about 14L liquid to reach just below the mesh pot.
I switch nute buckets every 7-8 days max and the plant has a huge, healthy root ball. The nute temps are always between 17-20C.

The thing is that since it is happening on both the hydro plant and the soil plant, the cause should be something that they both share, such as the environment conditions or the tap water used, or maybe it's the natural process as autos reach their end.

I don't plan to make any changes except that I have raised the light several inches. But I suspect that it may have something to do with the light, heat and maybe the fans also causing a bit of drying because of the tight space in the tent, but I don't want to risk mould by reducing the fans.

GhostBud420 said:

if your this close to harvest i wouldnt want to change much. just keep it as simple as possible before u start your final flush

Click to expand...

Thanks.
What sort of final flush is needed with hydro?
The plant is taking in about 4L water a day so If I just fill the bucket up with plain water a couple of days before harvest, the plant should flush itself ok.
I was wondering whether to use a flush like canna flush as well?