Magnesium deficiency?

[Spacedude22]

This auto is in the 3rd week of flowering stage, and the main cola has yellow leaves with brown spots. I'm guessing it is a magnesium deficiency. Just looking for some pointers and knowledge on how to fix this problem...thanks!

 

[Grow Bro]

Maybe add calmag ??

 

[Scientific]

What are you feeding it? What are you using for water? If not RO, how many PPMs?

 

[Spacedude22]

The whole veg stage I fed it Micro, Grow nutes.
In the flowering stage I started off feeding it
Micro, Grow, Bloom.
Then added Big Bud in the 2nd week. Then added Bud Factor x and Nirvana in the 3rd week of flowering stage.

 

[Spacedude22]

I also feed it 6.4 ph water every other watering

 

[Scientific]

What's your water like? How hard? Or do you use RO?

 

[Spacedude22]

I just use ph down on water until I get it at 6.4

 

[Scientific]

I just use ph down on water until I get it at 6.4

It's helpful to know the conductivity of your water, and thus how "hard" it is, which gives an idea of how much mineral content it has, which is often the level of calcium and magnesium. If you don't have a conductivity meter (they're cheap), then getting you water info at your water utility website can help.

If your tap water is very soft (like mine is--23 PPM out of the faucet) or if you are using reverse osmosis water, then you are at risk for developing a calcium/magnesium deficiency.

Those brown spots can be suggestive of Ca/Mg deficiency, but there is chlorosis too (lack of pigment), which can be from a bunch of things if you look at the symptom charts, but I think is most commonly associated with not enough nitrogen.

What is the starting pH of the water out of the tap? How much pH Down do you need to add to get your water to 6.4? High initial pH and/or lots of pH Down to correct suggests a lot of mineral content and less chance of Ca/Mg deficiency.

 

[Spacedude22]

I don't really have to use a lot of ph down, the water starts at around 7.6 ph out of the faucet. Could I use calmag nutrient to help fix the problem?

 

[Scientific]

I don't really have to use a lot of ph down

I was expecting an answer in milliliters per gallon.

the water starts at around 7.6 ph out of the faucet.

That's a little alkaline, which might mean you have some Ca/Mg in your water.

Could I use calmag nutrient to help fix the problem?

It sounds like it couldn't hurt. Remember to add calmag first when mixing nutrients.

BTW, those damaged leaves will not "get better." New growth will be what you need to watch.

I strongly suggest reading all you can about the nutrients you are using and about water and fertilization in general.

Good luck!

 

[Spacedude22]

Sorry I usually ph water by the liters, and I'll give it a try thanks for all the help!

 

[Scientific]

Sorry I usually ph water by the liters, and I'll give it a try thanks for all the help!

If you could post your results in a follow-up, it would be interesting to see how it goes. (And please do double check your fertilization regimen to make sure there's not a good that's giving your plant too little to eat. So easy to do...)

 

[Spacedude22]

Sounds good, will do! Thanks a lot for the help