burning/dying lower leaves 4 weeks into flower

[spaaaaceboy]

Hi Farmers,

Having some very bad burning and dying off of lower leaves and also some yellowing. This is a huge plant with 3 600's around it in 5 gal of coco eating once a day at 600-700pm. My temps are a little high getting up to 85 and a low of 69, but plants are off the floor. If anyone has any ideas I really need to save this girl. Thanks!

 

[Seamaiden]

Looks like it could be K+ to me, or overall overfeeding. I know you say you're only feeding 600-700ppm (I don't care for the ppm measurement, too imprecise), but the plants don't care about the numbers. I would seriously back off feeding, and when reintroducing it, give only really P, and a small amount of N (along with Ca and Mg since it's coir cultivation).

Basically, my first impression is burned due to overfeeding, but all that mid-plant necrosis sans yellowing is indicating a K issue, and K+ is where my gut is suggesting we look here.

 

[spaaaaceboy]

Thanks for replying Sea Maiden. I tried giving a lower dose of nutes, this time around 500ppms. I'm only using calmag plus and dyna gro bloom, so not really a way for me to adjust the ratios too much, but plant is still suffering pretty bad. Do you think I should go even lower on my feeding and any idea on how much calmag i should be using? Thanks!

 

[Seamaiden]

I would switch feeding the Cal-Mag through roots to foliar applications, and I would start with a half dose (as you would otherwise use for root feeding). I would try dropping ppm's to 300, you don't want to go too low or too quickly on that, but no lower than 250 using the .5 conversion factor. Are you able to take a look at the roots/root zone?

Actually, looking again at your pix, you're looking at the finish line, aren't you? I mean, they look DAMN frosty and damn near ready to finish up in the next couple of weeks or so to my eyes. Maybe, if that is indeed the case, you might want to just go ahead and start dropping the ppm's to 250 and then reduce to almost nil through the last week. That's what I do instead of going through the whole rigamarole of flushing.

Anyway, the plant is absolutely not dying, she's just having a rough time of it.

 

[spaaaaceboy]

Ok I will give a try, thanks again!

 

[BuildandGrow]

This is a large plant! I would say that she can take a large amount of nutrients. 600-700 does not seem high for being around half way through flower, in my opinion. I would be pushing 1000, depending on the nutrients you are using. What is the PH of your water?

The size of the pot is an issue. With a plant this size, I would recommend nothing smaller than a 10 gallon. A bigger root system and more room is needed for larger plants. Bigger roots WILL equal bigger buds. With that said, be sure to break up the root balls when you re-pot throughout your cycle. This allows the roots to spread through the new pot. If this step is skipped, you will not be maximizing all of the space in your larger pots. This is an important step that many soil/coco growers miss.

The temperature of your room is high. I assume that you are not running CO2 so your room should be no higher than 78 degrees. I would aim for mid 70's.

Root bound plants could show these symptoms that you have. I have also seen some fungus that makes leaves look this way.