Help needed - yellowing and brown dots?

Hello folks,

I'm hoping you can help me.
One of the plants I'm growing this year has started to have some leaves turn very yellow and have brown spotting. Also a purple stripe in the main stem has shown up, which reminds me of my Bloody Skunk as it was turning purplish but as far as I know this strain doesn't have red/purple genetics.
She is clear of insects as far as I can see, and I've used a parasite preventative spray just in case. The same with mould etc.

Some info:
She's a Pineapple Chunk feminised photoflower.
She's in coco coir with gravel added for drainage.
She's in a greenhouse with a heater and fan attached to an inkbird.
No additional lighting used.
Watered daily and biobizz nutrients added once a week.
Soil ph 6.5


Any insight would be appreciated as this is only my second year growning.

I have two other plants beside her (Apple Betty and Runtz Gum) and they don't have this.

You're washing out the calcium from the coco. You should be feeding daily to substantial run off..........with a nute solution pH around 6.0.
Frankly I'm surprised the plant is doing as well as it is.
Good luck.

MickFoster said:

You're washing out the calcium from the coco. You should be feeding daily to substantial run off..........with a nute solution pH around 6.0.
Frankly I'm surprised the plant is doing as well as it is.
Good luck.

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Feeding daily?
The nutrient type I'm using says to feed once a week for coco coir , and to keep the ph from 6.2 to 6.5:
https://www.biobizz.com/wp-content/uploads/2020/03/Nutrient-Schedule-EN-2020.pdf

I will try adding some cal mag and upping the feed to see if that helps.

Out of curiosity, wouldn't my other plants have this problem as well if it was a case of a nutrient issue?

You're certainly welcome to do as you choose. But according to most coco forums, most coco growers, including myself........coco should be fed daily. I feed daily starting around day 3-4 from sprout, and twice a day in flower. Some growers feed multiple times a day.
Not all plants react the same to the same nutes. My last grow I had one plant that was a problem from day one and the other 3 were perfect.
Just letting you know how I do things.

I googled "can plain water wash away calcium and magnesium from coco?"

Yes, plain water can wash away calcium and magnesium from coco coir by displacing potassium and sodium ions that the coco has absorbed during buffering. This creates an imbalanced nutrient state in the coco, as the medium tries to rebalance its cation exchange sites, potentially leading to deficiencies in the plant and a buildup of potassium. To maintain a healthy growing environment, it's essential to provide a consistent nutrient solution with sufficient calcium and magnesium to balance the coco's natural properties and prevent these issues.

i agree with mick, when i grow in coco minus new popped seeds i feed daily unless i notice burn

It’s been a while since I grew in coco, but the basic rules were never water with plain water, always feed, and never let the coco dry out. I would feed 2-4 times a day.

Dang... and here I thought they were doing great on a weekly feed... that's what I get for following instructions! I do water daily to runoff.
Lord knows how big they'd be getting if I'd been feeding them more!!

Okay ladies, brace yourselves for a flowering phase feast I guess!

Beautiful plants.......good luck with flower.

I’ll ask the others give their opinions as well, but I think you would be wise to cut the nute dosage in half when switching at first and see how they respond. When feeding that often they won’t need as much each feed.

Hook Daddy said:

I’ll ask the others give their opinions as well, but I think you would be wise to cut the nute dosage in half when switching at first and see how they respond. When feeding that often they won’t need as much each feed.

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Absolutely, I'll slowly increase and see how they take to the extra feed. Fingers crossed!

Thank you for your help.