Leafs yellowing/dieing all over /w pics

[Bubkuk]

Hey all, I've got 6 plants about a month into veg. It's my first grow so I am not sure whats happening to one of my plants. Over the weekend one of them starting looking rough. About half the leaves turned yellow. the tips turned brown. The plant wasn't taking in much of it's water. The other plants go through 2 galons in about 2 days, and this one is barely consuming any.

6x3 room.
1000w hps
ac unit to combat the heat
humidity 50%
Temp 74-80F
Soil grow, potting soil
Standard set of well rounded ferts giving once a week.
It's hard water here.

Pics:

Looking at the grow pics it's either heat stress or fert burn but my noob eye can't make the call. Help

 

[Paladin]

My guess would be fert burn. 74 - 80 degrees isn't hot enough to do that kind of damage. 74 - 80 degrees is optimum temps.

 

[Janjaweed]

yup, gotta be bad stuff going on in that soil!

too much nutes, possible ph or salinity lockout?
needs to dry and get flushed very well... or maybe repot it into bigger fresh soil.

could start flowering once its feeling better too..

 

[Bagzgroove]

Yeah I think you have nute burn too. . . give her a good flushing. . .

 

[RooRman]

Check your soils pH. 6.5 is optimal, over 6.5 is where you will start to run into nutrient lockup.

My guess is actually Mg (Magnesium) deficiency. Mg lockout can be caused by too much Ca (Calcium) which is what makes hard water, hard.

This can be corrected with Epsom Salts 1 tbsp. per gallon. Or a foliar feed of 1/2 tsp. per gallon.

Refernece this thread Trouble Shooting with pics for more information.

 

[Bubkuk]

Thanks for the replies all, I actually gave that one a 1 tsb per galon dose of epsom salts with a good flushing, and all the other ones a half dose just to be on the safe side. The problem doesn't seem to be getting much worse since doing that 2 days ago now.

What do I do with the bad leaves, remove them, and when should I try giving them more ferts again?

 

[RooRman]

I would trim off the dead leaves. There is more than enough other healthy ones to make up for them. The plant cannot repair damage that extensive, so trimming the leaves will help it.

 

[berrydizzle]

Yo man how big are the pots that you are using. 2 gallons in 2 days, thats way more than I am watering. Do you have any runoff or not. Just thinking I might not be watering enough. I have 3 gallon pots and here in the later weeks of flowering I have been giving about 48oz per plant every time I water, with little to no runoff.

 

[Bubkuk]

They are 3 galon pots. I water them enough so I get a little run off but not even enough to overfill the plastic dish they sit in. I think the heat from the bulb are helping them go through the water faster.

Update on the plants, they've stablized a little but the one in the pics looks pretty bad. I found the ph of the soil is sitting around 6.2 or so and the water going in sits at 7.2.

I am thinking about giving them some ph up the next time I water them see if that helps as the epsom salts don't seem to be doing too much.

 

[Herban Legend]

That plant in your pic looks like its suffering from root rot.
Somewhere down the line this plant got sick and stopped taking in water and instead part of the root mass rotted.
Water the other plants but stop watering this plant, your drowning her.
If you look at the whole plant and not the damaged spots you will see that most of the plant is a very light green while just a very small portion is more of a normal green. This means nutrients are not being delivered properly to the plant(nute lock).
Since ph is between 6 and 7 it tells me you have root rot.

 

[Bubkuk]

Intresting should I try transplanting her once she's dried out?