Clones start getting yellow leaves

[LausbuamProject]

Not sure what is happening here, 1 week after planting my clones into the coco slabs they start developing yellow leaves from the edges inwards.

My setup:
Nutrient solution: 1,2 EC (Canna Coco), 6,0 pH
Coco slabs: Canna CoGr.
Light: 400W MH for 2,9 m²

Basically I did everything as usual, the slabs were used in one previous grow without problems, were buffered and flushed afterwards. Nutrient solution should be fine too since I am also using it for my mother plants. So I suspect there is a problem with(in) the substrate. My only explanation would be fungus gnats. Could fungus gnat larvae damage look like that? Got very persistent ones this time, while I could reduce their number I couldn't get rid of them completely neither with nematodes and nor with Diflubenzuron later on.

 

[HempKat]

I'm sure fungus gnats didn't help things any but since they mainly attack the roots in their larvae form I'm thinking it's unlikely that would lead to just yellowing, it would be more likely to lead to just stunted unhealthy looking growth. Unfortunately there are quite a few things where yellowing in the leaves is a symptom. My guess is it's a magnesium deficiency since coco pretty much requires calcium magnesium supplementation. Now one would think a coco specific fertilizer would include additional Calcium and magnesium and maybe Canna Coco does but it's a general truth that cannabis needs a fair amount of calcium and magnesium and that most fertilizers don't have enough. So you might just need to include a separate cal/mag product into your feeding routine. Also you didn't say this but if you're using RO water then that's another thing that can force cal/mag supplementation as most tap and well water has some calcium and magnesium in it but RO water strips all that extra stuff in the water out.

Is a 6.0 ph what you usually have? Even on the grows in the past where you didn't have yellowing? I ask because they say that the ph for coco should be treated pretty much the same as if you were growing full hydro style. Which if true then a ph level of 6.0 should be fine. Now I've never grown in coco but I have seen lots of people who have had trouble using coco and it often seems like when they try to keep hydro like ph levels they end up getting deficiencies. If coco needed a more soil like ph then 6.0 would tend to lock magnesium out at 6.0, in soil magnesium gets locked out below 6.5

 

[LausbuamProject]

I used the Canna buffer agent before re-using the slabs, which is a Ca + Mg buffer solution, so there shouldn't be any take-up of calcium and magnesium uptake by the coco substrate. Therefore it would surprise me if that was a Mg deficiency. Or any deficiency at all since I didn't change anything with my fertilizing scheme. Just using tap water (EC around 0,4). Yes, I have always been running my system with a pH around 6,0.

 

[Creeperpark]

Your problem is a pH issue. Tap water is a problem in some cities and will cause the pH to rise. Adding acid will only hold the pH in a lower state until the hydrogen leaves and then return to the original pH. If you use a buffer solution with tap water you can run into problems. Try using the buffer with RO water and see if that will fix it. When using buffered RO water, the nutrients are much more available and plants will grow much bigger and faster.

 

[legalizeRO]

One of the easiest plants to clone, in my opinion.
A cup of tap water, 19-24 Celsius, water changed daily, 100% succes, cheap, even if they look like this:
I think it's Orca I sprinkle from a salt dispenser on the roots before I plant.
The box was destroyed a few years ago. Not even sure it works anymore.
But the roots are there, and so are the results.
I use to put painting tape on the tip of the leaves because they kept flexing and jumping out of the cup, resulting death.

 

[Creeperpark]

One of the easiest plants to clone, in my opinion.
A cup of tap water, 19-24 Celsius, water changed daily, 100% succes, cheap, even if they look like this: View attachment 18125324
I think it's Orca I sprinkle from a salt dispenser on the roots before I plant.
The box was destroyed a few years ago. Not even sure it works anymore.
But the roots are there, and so are the results.
I use to put painting tape on the tip of the leaves because they kept flexing and jumping out of the cup, resulting death.

Those don't look very vigorous and you lost some time. However, I can't argue with 100% success rate. Thanks for sharing.

 

[stiff]

I'd say check your runoff ec next watering and go from there. Or if you have one if those ph probes which measure in the substrate, measure right there.
And maybe check for fungus gnats larva. I just found out they're huge and easy to spot by eye. If there should be any..give them a slap with Bacillus Thurengensis Israelis (bti) and they will be a thing of the past,but I think you would be seeing flies by now. Anyway..that stuff really works and is no chemical shit

 

[legalizeRO]

Those don't look very vigorous and you lost some time. However, I can't argue with 100% success rate. Thanks for sharing.

Actually, I was very high also when posting this. I appologize !
I remember I was trying to replay to the title and show how bad they look and they nevertheless bounced back once they're in good soil.
These blondes were actually rooted in a water pump thing sprinckler/cloner, that I recently purchased.
They show roots faster (10 days, 14 in cups), less work as I change the water every 3 days, but for some reason they turn yelow really fast. The cup clones were way nicer looking.
But all that yellow turns back to green, not too long to notice how long it takes, or maybe because I'm not in a hurry...

 

[stiff]

If you would have given them an EC of
0.8-1.0 they wouldn't be yellow I believe. Try that next time. You probably gave them water only,right?