My carer has a grow on, is reticent to post here and has a slight problem. John Innes No3 compost, 400W HPS, growing between 30C to 33C. Any idea what this leaf damage is?


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Looks like heat damage + a Mg deficiency to me.

30-33 is too hot man. 28 is about the max you want to let it go (20-28 is ideal sort of range).

Have you given them any epsoms?

Oh and how close is that light?

No Epsom Salts. The light is two foot from top leaves.

Canna Vegga

Cuttings, rooted for three weeks just had first feed. 1ml per liter

When did the tips start going like that? Did your plants show signs of nutrient defs. before you gave them the feed? What stage are these plants at?

It's definitely too hot for them - do they have extraction + intakes (passive or active) in there?

I think misting with epsoms is definitely in order.

Tips were yellowing before the first nute. He is getting a 4" inline fan, at moment 4 PC fans are being used.
+ oscilating fan

Is that 30C when the lights are off ?Do they get any fresh air?When are they watered and fed?How warm is the water?How old are they and what the pot size?

With the 4 pc fans extracting? Are there passive intakes there too (eg. slits/gaps in the bottom of sheeting covering your area, leading to some fresher source of air), or is it all sealed?

Decent extraction should sort the heat problem really. It's more important than having active intakes, but you do need some kind of intake to get that air exchanging...