What is causing this yellow/brown spots on the leafs?

[cogollo]

Hey everybody.
Do you know what is causing this? https://www.icmag.com/ic/album.php?albumid=33756&pictureid=789564
I grow in coco medium with canna nutrients at 6.0 pH. Using 600w light, plants about 50-60cm under it.

I had a little problem during three days with really low temperatures, down to like 7c but thats under controll and know its 17c for the night and 26 for the day. Plants are 3 days in to flower.

Thanks in advance!

 

[CannabisFox]

hey cogollo

first i'd like to say that night temperatures are best not 5°C under day temp~slower growth.
the ph should fluctuate between ~5.3-6.0 to make sure all nuts are in best range from time to time.
I would say that your rh is very low and you maybe have a p deficiency. But im not sure!

Greetz
CF

 

[PoopyTeaBags]

you need to give more information... like ppms, nutes etc....

 

[el dub]

Looks like they need a shot of cal/mag to me.

lw

 

[cogollo]

Hey and thanks for answers.
I dont have the exact ppms but I use the growschedule from canna..
Worth to note is that I have pretty hard water... Its not to low RH, its around 80 during night and 60 day time..

 

[el dub]

Micro nutes is the answer here, imo.

No need for any tests other than reading the canna bottle to see if'n it contains any micronutes. (I bet it doesn't.)

lw

 

[cogollo]

Getting worser..........Root aphids? I had problem with them before but not this serious, dont know either if this damage looks like root aphid damage?

 

[CannabisFox]

You should do what el_dub suggested.

but you really need an ec-meter IMO

edit: if you are working with tap water which is quite hard that could be the prob... maybe it also contains too much chlorine? ....

 

[Toes.]

too much calcium locks out magnesium.

 

[spiritual g]

the cold nights for certain strains that low can lead to poor nutrient uptake,so that could be the major factor in this,possible root damage too if sensitive.Canna coco a and b is a one nutrient feed with everything you need for a full grow and in a two part form with all the micro nutrients you need.Make sure you are mixing your nutrients properly also.peace

 

[cogollo]

Getting pretty damn frustrated. I had my temps in order but the problem will just continue....

 

[SeaMaiden]

the cold nights for certain strains that low can lead to poor nutrient uptake,so that could be the major factor in this,possible root damage too if sensitive.Canna coco a and b is a one nutrient feed with everything you need for a full grow and in a two part form with all the micro nutrients you need.Make sure you are mixing your nutrients properly also.peace

This^^^
I have too much experience trying to grow in a cold room. What you're depicting doesn't look like any Ca/Mg problem I have ever seen. I see a slight problem with P, but the rest of it doesn't fit with Ca/Mg issues. My problem in trying to help you is that I always have to use Google to convert the temps. 7C for overnight temps is WAY too low. I bet it takes a while for the room to get back up to sufficiently warm temps, which may be at the heart of the problem.

This absolutely does NOT look like a root aphid problem. I would first get the temps up, especially overnight temps.

Edit: 17c is still too low. Get the temps up. Also, let the pH range, 5.8-6.2.

 

[cogollo]

Hey everybody...Well I doubt its the cold nights, first I just had 7 degress during 3 nights, now its 17 during the night, i have plants in an other location where the temps never raise to over 18 during the day and 9 during the night - and they dont show this symptoms......
Anyway, still dont know what to do, have watered with other pH, 5,5 5,7 and 5,9.....

 

[cogollo]

Hi again! A friend of mine thought it could be a phosphorus AND potasium deficiency/lock out. I have watered with a lower pH but it havent helped yet. Can i give the plants a shot of pk 13/14 even though the plants just are 9 days with 12/12?

 

[SeaMaiden]

I have already offered my opinion and you dismissed it. It does not look like a P or K problem that I have ever dealt with. Perhaps your friend is right, but I disagree based on my own experience. Why don't you try raising the temps a bit, see what happens? It's well established that root zone temps must reach a minimum level in order for nutrients to be utilized.

 

[cogollo]

Hi, yes thanks for your opinion, i have watered with diferent pH levels two times per day. Anyway problem seem to be solved, new growth are real green and healthy. I dont know but could have been some lockout from those days with so cold temps. Still not able to uper my nights temp. I live in a really cold zone, already using a 1000w warmer in the room where i have the clones and wich in the tent with the plants are located....Well anyway i hope it will continue without problems. And again thanks everybody for your help, i will tri to upload some pics tomorrow for you to se......Another question if anyone know, is it a big loss to flower with mh instead of hps?

 

[SeaMaiden]

Wanna know what I did? I took a cheap electric blanket from Walmart, folded it up and used black contractor bags as a pillowcase and put that under the pots. Warms up the root zone without expending huge amounts of energy, and as some law of thermodynamics states, heat rises, thus helping to warm the area. I also switched from closed hoods to vertizontal parabolics.

Metal halide is fine as long as it's the correct color temperature. <4,000K would be my recommendation, <3,000K would be better.