Please help diagnose my first plant!

[fasttanoy]

Evening chaps,

I've been growing Jack Flash in a 75/25 coco/perlite mix and it wasn't going too badly until on day 40 of flower the lower leaves starting forming these weird browny-yellow patches. In the last two weeks the problem has got worse and moved up to half-way with some leaves right at the bottom completely dead. The lower leaves are quite crinkly now and are nearly completely that brownish colour:

(you can see in the bottom right of the last pic what the lower leaves look like)

Can anybody help identify what the issue is? I'll be harvesting soon so I doubt there is anything I can do about it now but I would like to avoid the same thing happening on my next grow.

Searching around this forum it looks similar to some root rot pictures, however the plant is still really thirsty, she's about 1.3m tall in a 20 litre pot and drinks about 4 litres of water every 3 days. I've been feeding her using the Canna recommended nutrients at the recommended rate, plus some CalMag. I've also not noticed any bad smell from the leaves. The problem has reached the middle leaves now and gets worse and worse to the bottom of the plant where most leaves are dead.

Please help!

 

[NuttyProfessor]

hows your ph ? and did you ever flush this pant right out in between feeds and changing from veg to flower nutes , I know a lot of leaves die near harvest but yours looks more like theres a lock out , I could be wrong and has the heat been up more ?

 

[fasttanoy]

I've been fluctuating my pH between 5.6 and 6.1, I thought this could be the problem that I've been changing the pH too regularly so I've kept it at 5.8 now for the last few waterings.

I didn't flush because the flowering nutes are the same as the veg ones but in a higher concentration.

Yes there has been a heat wave here last week, the temperature in the grow room is consistently 80F

 

[NuttyProfessor]

i think you have a build up of unused nutes , give them good flush ,( double your pot size so 40 litres of water) , then feed in a bout a weeks time slowly again half the nutes you use, its good to feed twice flush once feed twice flush once and so on , try an extra fan if you can

Good luck

 

[fasttanoy]

i think you have a build up of unused nutes , give them good flush ,( double your pot size so 40 litres of water) , then feed in a bout a weeks time slowly again half the nutes you use, its good to feed twice flush once feed twice flush once and so on , try an extra fan if you can

Good luck

Thanks for that
I'll flush the plant tomorrow, could the build up of unused nutrients be caused from changing my pH every watering? Just so I know what to do different next time.

 

[Tardigrade89]

What is the temperature in the room where you grow?

Edit. Nevermind, I saw you wrote 80F.

 

[fasttanoy]

What is the temperature in the room where you grow?

Edit. Nevermind, I saw you wrote 80F.

Yeah that's right, it used to be around 76 but we've had a heat wave recently and it's now around 80F most of the time, I have my lights on at night to balance out the heat.

 

[Tardigrade89]

Hehe I feel you. Been having a heat wave where I live also. Somebody really need to invent a new heat resistant strain and call it Global Warming.