Any ideas what this might be?

not 100% sure, but maybe a cal/mag deficancy

They look dark to me, have you tested the ec run off?

It's a cannabis leaf

I would say heat burn

...some overwatering also

Looks like burn of some sort. Nutes or light.

mikeyboy2121 said:

Looks like burn of some sort. Nutes or light.

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I would say light! How often do you feed them??

Jenko said:

I would say light! How often do you feed them??

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I've had leaves look exactly like that when too close too soon to my led's.

mikeyboy2121 said:

I've had leaves look exactly like that when too close too soon to my led's.

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Exactly lol reason i know is cause i've done it myself.

We figured out its a fungus,
Whats the best way to clean a sealed room from a fungus like this?

wingerdinger said:

We figured out its a fungus,

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I dont think so.

Remove all plants, clean the room with cleaning stuff like chlorine.
Personally I think a fungus is the least likely option by far

wingerdinger said:

We figured out its a fungus,
Whats the best way to clean a sealed room from a fungus like this?

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Rust fungus? Didn't look typical of rust fungus.

To clean I recommend Physan 20.

How do i clean it out of my dehumidifier/aircon/ carbonfilter/fans?