Leaf spots

[egger]

Hello all,
I'm on my second round of growing at the minute, so am pretty much a newbie.
I learned a lot from my first grow, and from the advice given in these forums. However, one of my plants has got me a little concerned, and I haven't been able to identify the problem. I would really appreciate an expert eye to identify what's wrong, and maybe give some advice how to remedy.

The plant should be ready to harvest in around three weeks (according to Greenhouse Seeds) however It has yellowing leaves throughout (perhaps 25% of the plants leaves are yellow which then curl up and die within a week). These leaves have large brown spots. I have lots of buds forming, but am thinking that they should be packing on weight a little quicker. Not sure what to do right now.

Here's my set up and a couple of images.
- Plant is a Big Bang Auto by Greenhouse Seeds
- 3x3 tent with 260W COB LED's 18" above canopy. 18/6 schedule
- Good ventilation and temps kept below 80F.
- Grown in 3G smartpot. Use supersoil and generic base mix in pot (no slow release ferts in base mix). Some coco coir and perlite.
- Water / feed with aloe, coconut water, compost teas and sprouted seed teas. Teas include kelp and molasses. Everything PH'd to around 6.5. No bottled nutes.
- Negligible fungus gnats
- Another plant in my room (six plants total) has just two leaves with some similar brown spotting but no yellowing. Rest of plants are healthy.

Anyhow. I'd really appreciate any advice.

Cheers

 

[JigSaw]

Manganese or calcium deficiency would be my guess. Could possibly be a magnesium deficiency too but I doubt it judging by the spotting instead of linear discoloration. Spotting is a notorious late sign of manganese and calcium deficiency though.

 

[Dr GreenJeans]

Look into phosphorus since you're in fower atm and let me know what you're feeding, like your current ppms and the nutes you're feeding it atm.

Be mindful that spots can also develop from nutrient water being splashed onto the leaves. Just needed to be said just in-casies .

 

[egger]

Hi JigSaw,
Thanks for the info and the chart. most appreciated.
I have some dolomite lime in the garage. They are due a watering today. I'll give it a whirl.
Many thanks

 

[JigSaw]

Hi JigSaw,
Thanks for the info and the chart. most appreciated.
I have some dolomite lime in the garage. They are due a watering today. I'll give it a whirl.
Many thanks

Anytime. That's what this community is for. Spreading knowledge and tips about a plant we all share a common love for.

Cheers .

 

[Amadeus Forzin]

Look into phosphorus since you're in fower atm and let me know what you're feeding, like your current ppms and the nutes you're feeding it atm.

Be mindful that spots can also develop from nutrient water being splashed onto the leaves. Just needed to be said just in-casies .

This^^^^^^


Calcium shows as rusty spots and manganese displays from the newest growth first. I'd say it's a P deficiency.

 

[egger]

Dr GreenJeans, Mr Am4zin,

Thanks for the posts. I think you hit it on the head with the P deficiency.

I thought that coconut was high in P, like it is in K, and that this would be sufficient through flowering as i already have bonemeal in the supersoil. However, i found that K is about 6x more prevalent than P in coconut water. Perhaps my supersoil is not as heavy in P as i thought.

I potted my other 5 plants in the same soil, at the same time, but as these are photo's and still in veg, then this may explain why there is really only problems on the plant that is deep into flower. This could be whats to come for the photoperiod plants after i switch them so i'll get a hold of some PK fertilizer, treat the auto, and be ready during flower for the rest of them.

As for the ppm's, TBH, i don't really know anything about this. I grow in soil, and feed organically (aloe, coconut and teas), all with PH'd water, but have no idea about the ppms. Is this something i should check for a soil grow?

As always, i appreciate the advice!

 

[Dr GreenJeans]

Actually, I forgot you're in soil .
Disregard ppms in that case


Sounds like you know exactly what to do! And like you have a handle on it, let us know if you need anymore help

 

[killa4lyfe]

looks like you had nute lock out b4 u started the flip..i would start over...your have mag and zinc issues

 

[egger]

Thanks for the post, Killa4lyfe,

I'm only 2 weeks away from harvest (if you believe the breeder), but i think its probably three, maybe four? Either way, i'm close, so wont be starting over. I'll try and rescue what i have.

The plant actually looks a little better as of yesterday. I think the PK feed a few days ago helped. I'll keep a really close eye on them though.

As i mentioned, i'm a novice grower, so would appreciate your heads up how you diagnosed the Mag and zinc problems.

In fact, if anyone knows of a good, definitive book that i can buy for a reference guide, that would be really helpful.

Many thanks
Egger