Little brown/rusty spots

[Mango]

Hi guys, Ive looked through the forum and while i have found similar posts to mine I feel that i best post these pictures to get an experts eye on the case. I am in the 4th week of flowering. 400W HPS, 10L pots, watered every 4-6 days with bio-bizz nutes. About 1 week ago leaves started developing rusty brown spots on some of the older leaves. The problem is spreading and getting worse.
I have thrips and fungus gnats. They are dying off as i have put a layer of sand down on the soil to stop their life cycle and the sticky traps have not caught anything in a while.
Any insights would be appreciated


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[hotboxfox]

Hmm, I don't see any obvious sign of lockout, though I'd be wary and keep an eye on that now that you've got sand down. Any medium changes will affect overall pH.

Maybe a foliar treatment with a mild soap and water mixture? Perhaps a plant-safe fungicidal spray, preferably natural or organic?

With how far you are in with flowering, I can't tell you to use the spray concoction I usually use - a combo of boiled garlic and tobacco. Works rather well but stinks to high heaven and can last upwards of a month in smell. I only use it in the vegetative stages, though, and no later than two weeks after flowering. After that, I stop immediately and gently wash the plants.

Good luck!

[cocohead]

How much are you feeding and how long were they vegged for? What strain?

[Mango]

I was feeding them 1ml veg and 1 ml bloom. As to the strain, I have no idea as i found these seeds in some weed last year. two of the plants are on their 3rd bloom now and they give a really nice smoke :)

[cocohead]

What soil are they in?

[Mango]

they are in J arthur bowers multi purpose. they were vegged for only a short time. They were cuttings and as soon as they had rooted they went to 12/12

[cocohead]

I don't want to say for sure but it could be a deficiency. are there any brown leaf tips?

[Mango]

There may be a very few leaves with brown tips. I cant check now as my girls are sleeping :)

[Hashassin]

Almost certainly a general deficiency I'd say (if you're still on 1ml of each)

This is one schedule that quite a few people have followed..

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"Once you are on 12/12 start feeding 1 ml of both Grow and Bloom to a litre of water.

At about week 2 of flowering change the mix to 1 ml Grow and 2 ml Bloom per litre.

At week 3 [21 days] a one off feed of a heaped table spoon of epsom salts per 10 litres add to that 1 ml of Grow and 2 ml of Bloom.

Round the 4 week mark, the mix is 1ml Grow and 3 ml Bloom.

Once you start to see browning of pistils change to 2 ml Grow and 1 ml Bloom, keep with that till the end."
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Biobizz's own schedule builds up to 4ml of Bloom + 1ml Grow for the last three weeks, though that can be a bit excessive.

[munkman]

check temps when lights are off keep them above 16c!