HELP!! One of my Plants is Dying.. Take a Look!

i am stumped about the problems on one of my super lemon haze plants which could be dying. i have 2 plants which are 7 weeks and 4 days old from sprouting. both have exactly the same of everything but only one is turning yellow and brown and crispy.


its the one in the blue tray, the one to the right is the other one the same age, the rest are nearly 2 weeks younger. both been topped last week but problems were appearing before that.

under 400w metal halide around 18-20" away.

miracle grow multi purpose compost in 11l pots. 20% perlite and a cup of lime in each

only had water, no nutes yet.

temp around 80-83

humidity around 40-50 but has been as low as 30.

its the 4 main fan leaves that are affected, mainly the bottom 2.


this is the same leaf in both pics. all yellow with green speckles and lots of brown which started in the centre. the right hand leaf is pretty much gone and would crumble if i pinched it.



this is the other bottom branch main fan leaf, not as bad but yellow and quite a bit of brown.



these are the upper 2 main fan leaves which are yellowy with brown bits dotted about.

the rest of the plant is pretty much ok, mostly a really nice green.

can anyone tell me what they think the problem might be?

cheers!

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PH of water? Nutrient deficiency from nutrient lock out perhaps.

The Miracle Gro is pre fertilized?

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Just looks like nitrogen def., most obviously because of yellowing moving from bottom to top of foliage.

soil ph is just under 7 , only got a crappy soil ph meter which doesnt measure the water properly i dont think.

yes lots of fert in miracle gro compost which is why i aint fed them yet. think i should start feeding quarter or half strength?

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Terry there's a good probability that you have the wrong PH in your root ball, causing nutrient lockout - including (but perhaps not limited to) the nitrogen deficiency that Balzac pointed out. I would go buy a proper PH water pen rather than relying on a soil tester.

If it were my plant I would either:

Flush with distilled water - PH of 7 - flush with 2X pot volume. Buy a ph pen and let the pot dry out, ph adjust the water for next feeding. Raise the pot so it's not sitting in water and let dry.

or

Buy a PH pen and flush with a mild, 1/8 - 1/4 strength, fertilizer solution. Raise the pot and let dry.

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This is a good no-risk step that may solve the problem and will not hurt anything. This may just be the first plant to show symptoms, don't be too concerned if it starts in others. The damaged leaves will fall off and die, don't worry about it - they're low on the plant.

ok mate, thanks for your advice!

i had that problem, i used cal-mag and in a week it showed signs of improment. no hope for that yello leaf. when its ready to come off it will.