Light or Nut burn, Struggling to diagnose

[Fen78]

Metrics first: 3*3 grow tent, 400w vivosun aerolight, light is 30" from plant, PPFD is 580, 2 plants growing in DWC (one plant in soil) , Feeding GH six part series and using at 50% recommended dosage (except CalMag which is full dose) for week 5 feeding schedule. Plants are all purple haze. all other environmentals are spot on.

So this if my first grow and everything was going swimmingly well up to a couple weeks ago when I ran into magnesium deficiency in my oldest plant being grown in DWC. I corrected that (nutrient mixing order) and everything seemed to bounce back. Now on my oldest plant ( they are all about a week apart) all the new growth that is exposed to light is getting ever so slight yellow tips. The new growth that is shaded by fan leaves or not receiving as much light do not show the yellow tips. I originally thought light burn but none of the other plants are showing this issue. I know a problem doesnt always have to be universal but it makes sense if one is getting light stress/burn why wouldn't the others. Granted the PPFD is lower on the other plants due to their distance from the light but still. After doing an exhaustive search it seems maybe it could be a combination of both? Anyway I am struggling to come to a definitive answer and thought I would reach out to the hive mind for some perspective.

 

[Grownsince95]

Those tips don't look burnt to me, sometimes a lower vpd doesn't pull calcium up fast enough for the rapid growth. Also, I think actually turning your light up a little will kickstart some transpiration which will also help with that.

What's temp and humidity like?

When you say half the recommended dose, GH has 3 "levels" of feed... what's the EC/pH going in the buckets and does it go up or down?

 

[Fen78]

Those tips don't look burnt to me, sometimes a lower vpd doesn't pull calcium up fast enough for the rapid growth. Also, I think actually turning your light up a little will kickstart some transpiration which will also help with that.

What's temp and humidity like?

When you say half the recommended dose, GH has 3 "levels" of feed... what's the EC/pH going in the buckets and does it go up or down?

Huimidy has been an average at 60% (dropping to 52% during dark) and temp has run an average of 77.6 degrees with a night time drop to 69 degrees. VPD fluctuates between 1.3-1.5.

So I should say I am running the Intermediate feeding schedule from GH. I am checking PH twice a day (morning and evening) and keeping it between 5.8 and 6.2. The trend has been increase in PH between checks. Usually will go from 5.8/5.9 in the morning to 6.3/6.4 by evening. PPM has been between 600-800. Oldest plant is 6 weeks old, going to let them all veg until the end of the month to allow the younger plants to catch up before switching to flower.

 

[greengrower73]

Those tips don't look burnt to me, sometimes a lower vpd doesn't pull calcium up fast enough for the rapid growth. Also, I think actually turning your light up a little will kickstart some transpiration which will also help with that.

What's temp and humidity like?

When you say half the recommended dose, GH has 3 "levels" of feed... what's the EC/pH going in the buckets and does it go up or down?

" a lower vpd doesn't pull calcium up fast enough for the rapid growth "

I have been at it as long as you have but this bit of info solves a small mystery I had this grow with 1 plant of 4 having low Ca issues, back left plant in my 5x5, cooler than the rest and it was through the coldest part of the season. Soon as the temperature went up my leaves on that plant cleared up. Now in flower you'd never know they had an issue. I thought it may have been strain related just demanding more Ca but too cold and low VPD may have contributed to the spots and leaf fading typical of a calcium deficiency

 

[Grownsince95]

Ok so at that level if you're feeding full strength calmag and 1/2 strength of the rest, the calmag will be taking up a lot of your EC. What other 2 parts are you using in addition to those 4?

I think your plants look good and a few yellow tips here and there is just something to keep an eye on. That big plant might want some cleaning up and more air moving through it but otherwise your numbers seem ok

 

[Ninjadogma]

Huimidy has been an average at 60% (dropping to 52% during dark) and temp has run an average of 77.6 degrees with a night time drop to 69 degrees. VPD fluctuates between 1.3-1.5.

So I should say I am running the Intermediate feeding schedule from GH. I am checking PH twice a day (morning and evening) and keeping it between 5.8 and 6.2. The trend has been increase in PH between checks. Usually will go from 5.8/5.9 in the morning to 6.3/6.4 by evening. PPM has been between 600-800. Oldest plant is 6 weeks old, going to let them all veg until the end of the month to allow the younger plants to catch up before switching to flower.

Is your EC dropping as the pH goes up? If so, it's supposed to be a sign the plant is eating normally. If EC is relatively static and pH goes up it could be bicarbonates in the water. Are you using RO?

 

[greengrower73]

Metrics first: 3*3 grow tent, 400w vivosun aerolight, light is 30" from plant, PPFD is 580, 2 plants growing in DWC (one plant in soil) , Feeding GH six part series and using at 50% recommended dosage (except CalMag which is full dose) for week 5 feeding schedule. Plants are all purple haze. all other environmentals are spot on.

So this if my first grow and everything was going swimmingly well up to a couple weeks ago when I ran into magnesium deficiency in my oldest plant being grown in DWC. I corrected that (nutrient mixing order) and everything seemed to bounce back. Now on my oldest plant ( they are all about a week apart) all the new growth that is exposed to light is getting ever so slight yellow tips. The new growth that is shaded by fan leaves or not receiving as much light do not show the yellow tips. I originally thought light burn but none of the other plants are showing this issue. I know a problem doesnt always have to be universal but it makes sense if one is getting light stress/burn why wouldn't the others. Granted the PPFD is lower on the other plants due to their distance from the light but still. After doing an exhaustive search it seems maybe it could be a combination of both? Anyway I am struggling to come to a definitive answer and thought I would reach out to the hive mind for some perspective.

What do you mean by " soil " ? a bunch of varieties and brands. Promix, Sunshine mix#4, Happy Frog, Coast of Maine. ect. I use a Promix type peat based mix plus added perlite, worm castings + a few other additives. I never have to PH my liquid inputs, those soils have buffers that help stabilize the soils ph.

In my autopot system I still don't PH and I use the same GH nutes, Most of my plants don't need cal/mag until weeks 2-3 in flower when their demand for Ca goes up. I supplement Mag with Epsom Salts at 1 tsp/gal through veg.

Burnt tips come from too much feed and not enough light, or too much light and not enough feed. An expert grower once told me that if you are not burning your tips you aren't trying hard enough.

 

[Fen78]

Is your EC dropping as the pH goes up? If so, it's supposed to be a sign the plant is eating normally. If EC is relatively static and pH goes up it could be bicarbonates in the water. Are you using RO?

To be honest I haven't been checking EC in conjunction with PH checks, only when I mix nuts. But I will be adding that to my daily tasks when I check PH, so thank you for that bit of info!!

 

[Fen78]

What do you mean by " soil " ? a bunch of varieties and brands. Promix, Sunshine mix#4, Happy Frog, Coast of Maine. ect. I use a Promix type peat based mix plus added perlite, worm castings + a few other additives. I never have to PH my liquid inputs, those soils have buffers that help stabilize the soils ph.

In my autopot system I still don't PH and I use the same GH nutes, Most of my plants don't need cal/mag until weeks 2-3 in flower when their demand for Ca goes up. I supplement Mag with Epsom Salts at 1 tsp/gal through veg.

Burnt tips come from too much feed and not enough light, or too much light and not enough feed. An expert grower once told me that if you are not burning your tips you aren't trying hard enough.

The plant in soil (Fox Farm coco-loco) is doing just fine, and my nutrient schedule is different than the those growing in DWC. Its only the oldest plant in DWC that I am having issues with. I thought Hydro would be fun but now I am realizing soil seems much easier. But this why I wanted to try both.

 

[greengrower73]

The plant in soil (Fox Farm coco-loco) is doing just fine, and my nutrient schedule is different than the those growing in DWC. Its only the oldest plant in DWC that I am having issues with. I thought Hydro would be fun but now I am realizing soil seems much easier. But this why I wanted to try both.

It maybe easier but once you learn the dwc you can rock it. I think it by far out grows most other styles and the root mass they create can suck up & pump a lot of nutes through the plants like no other style I've seen. There must be some DWC folks here that can help. My res feeds through a water line to a tray plants feed from & I'm good with that but starting over DWC would be my go to. There are more parameters that need to be filled but once you have all of them covered you can out grow the rest.

 

[MrSativa]

If your roots of the dwc are fine it could have just been a ph slip up.
If this is your first run on dwc maybe add extra oxygen stone or bigger oxygen pump also keep root temp constant.

dwc is growing extreme but almost zero forgiving

how often you clean reservoir ?

 

[Fen78]

It maybe easier but once you learn the dwc you can rock it. I think it by far out grows most other styles and the root mass they create can suck up & pump a lot of nutes through the plants like no other style I've seen. There must be some DWC folks here that can help. My res feeds through a water line to a tray plants feed from & I'm good with that but starting over DWC would be my go to. There are more parameters that need to be filled but once you have all of them covered you can out grow the rest.

Dont get me wrong I really like the growth I am getting with DWC, however its been more hands on than I was prepared for. I have my eye on a re-circ system with a chiller so I can bump Co2 but and only have to do one res change between all the buckets. First I want to grow in all mediums to get some more hands on experience.

 

[Fen78]

If your roots of the dwc are fine it could have just been a ph slip up.
If this is your first run on dwc maybe add extra oxygen stone or bigger oxygen pump also keep root temp constant.

dwc is growing extreme but almost zero forgiving

how often you clean reservoir ?

Reservoir change is every 7 days and roots look fantastic. Considering all the replies here i think maybe a PH/nut slip up may be the culprit. Learning through mistakes!