HELP! yellow leaves falling, suddenly brown leaves

[italianguy]

Hi everybody!
I am growning outdoor (it's my first time) in a 14L (about 3 gallons) pot. I am growing autoflowering. TYhe plant is in full sun for about 12h a day and the temperature goes up to 29°C.
Slowly, the bottom leaves of the plant started turning yellow and falling: I took it as the sign of nitrogen deficiency, so about 10 days ago I started adding to the water about 1 tbs of KNO3 as to provide nitrogen, However, the situation is not improving at all and so I do not know anymore what could be the cause and I am posting here.

Before providing additional nitrogen I gave the plant about 0.3g daily of 10-10-10 NPK fertilizer, which came in small pebbles and I dissolved it in the water.
Today the plant quickly developed more issues: below some pics.

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These are all from yesterday: you can already see some purple-ish spots developing on the top leaves.

This is the situation today: look pretty critical to me.


I suppose I should prcede with a good flush, hoping to recover at least some of the yeld. Please let me know your toughts! Much appreciated.

Cheers

 

[SoOrbudgal]

Yes we try and fix our plants sometimes and we do abit of " over kill loving " Good to flush and i would not let it suffer from too much intense heat or sun move into shade for few days but do not over water. Just flush real good couple gallons then allow to dry in the shade. Couple days remove those affected leaf they will not recover damage is done or leave them on they will fall off. I hope this helps you i think you know what to do, she will recover but needs nothing but rest for a few days. Once she rests do not give nitrogen she does not need that amount she need potash, calcium, magnesium minerals and just a slight bit of nitrogen during flowering. Like a 5-10-10 ratio. I use a bloom mix of 5-10-5 NPK but i do use other products for when they are showing toxity like yours. Some countries are unable to find it but you do have things you can use to help bring health back to plants without spending alot of money.

toxic shock