Leaf Tips Issue: Yellowing w/brown, hard spots

[CheebaMeeba]

Hey all,

I am seeing some yellowing with brown, rough/hard spots on the tips of some of the leaves (mainly largest, middle fan leaves). Additionally, I have a plant that is showing some yellowing without the brown, rough/hard spots. See the pic below. I know, it is a shitty phone cam pick. I need to break out my reg cam and take some better pics. If anyone has any ideas, let me know.

FYI, these plants are 19 days old. I am using a 400w hps in a grow room that is 7.5x3x2.5 with a 425 CFM centrifugal fan and an oscillating fan.

I am using Dr. Earth POTing soil in 2-gallon buckets with a layer of vermiculite on the top of the soil. I do use filtered tap water that is in a 5-gallon bucket to let any chlorine attenuate. I put just under half a cap of superthrive in the 5-gallons of water (yes, I know there is a divide on the topic of superthrive). I water every 4 to 5 days.

Otherwise, the plants are doing well.

 

[Seamaiden]

Ewww... vermiculite? Sorry, I hate that stuff. Chlorine attenuation is a new one on me, I thought it just evaporates.

You don't really say much about the feeding, but off the toppamah head it sounds like you're describing a classic calcium-magnesium deficiency. And with soil a bit of dolomite lime, top-dressed for long term Ca/Mg feeding, is helpful. Also, worm casting tea will help provide both elements.

A quick fix that can help tease apart the problem, depending on what happens next, is to give a foliar feed of MgSO4 (Epsom salt) at the rate of 1/4tsp per gallon of water (include a surfactant). If the problem progresses or gets worse, then you have to include calcium in the equation. If it stops then it's just magnesium you're concerned with here.

However, none of this will be effective if feeding pH is off.

I forgot to add that IF you use very clean water (extremely low ppm) then dolomitic lime not only will dissolve in it, but it absolutely will go into solution and is immediately available to the plant. Dolomite lime provides Ca and Mg in carbonate form.

 

[CheebaMeeba]

lol...I normally use vermiculite, but think perlite will be better next go around.

All I am doing wrt feeding is just water with the superthrive. I thought that the Dr. Earth soil would keep them going with appropriate nutes until flowering. I have Dr. Earth Bat Guano for later veg, but wonder if that would be good right now?

I am new to all of this, so I appreciate the help with this.

I will try the epsom salt foliar feed, first.

Thanks for the help.

Ewww... vermiculite? Sorry, I hate that stuff. Chlorine attenuation is a new one on me, I thought it just evaporates.

You don't really say much about the feeding, but off the toppamah head it sounds like you're describing a classic calcium-magnesium deficiency. And with soil a bit of dolomite lime, top-dressed for long term Ca/Mg feeding, is helpful. Also, worm casting tea will help provide both elements.

A quick fix that can help tease apart the problem, depending on what happens next, is to give a foliar feed of MgSO4 (Epsom salt) at the rate of 1/4tsp per gallon of water (include a surfactant). If the problem progresses or gets worse, then you have to include calcium in the equation. If it stops then it's just magnesium you're concerned with here.

However, none of this will be effective if feeding pH is off.

I forgot to add that IF you use very clean water (extremely low ppm) then dolomitic lime not only will dissolve in it, but it absolutely will go into solution and is immediately available to the plant. Dolomite lime provides Ca and Mg in carbonate form.

 

[CheebaMeeba]

Better pics

Seamaiden, I posted better pics in my grow diary:



Let me know what you think. From what I have been reading, this looks like it could also be a potassium deficiency?

 

[Seamaiden]

Yes, potassium deficiencies can and do cause necrosis from the leaf TIP moreso than the margins. And it's not spotty the way calcium problems are. The reddened petioles are a sure sign of K uptake or utilization problems.

 

[CheebaMeeba]

Yes, potassium deficiencies can and do cause necrosis from the leaf TIP moreso than the margins. And it's not spotty the way calcium problems are. The reddened petioles are a sure sign of K uptake or utilization problems.

Thanks, Seamaiden, I appreciate the assistance. I have a ph soil tester that I will use to check for potassium deficiencies.