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Looks like you have at least phosphorus (reddish stems / veins everywhere) + nitrogen (bottom leaves yellowing and dying) deficiencies, if not other deficiencies as well. Measuring PH is a must, as it affects the uptake of all nutrients. You need to follow @Horticulturehobbyists advice, otherwise these plants aren't going to survive. If you are trying to avoid buying fertilizers, you can try experimenting with getting phosphorus from sources like boiling banana peels or nitrogen from diluted piss (https://www.royalqueenseeds.com/blog-how-and-why-to-create-homemade-organic-fertilizers-n764). Results will obviously be far less predictable though than with nutrients which have recommended dosages.

@Eryan, Thanks for your advice. I'm not trying to avoid fertilizers, I just want my grow to be as organic as possible. I couldn't find any organic fertilizers when I started this growth so I had to go with manure that had NPK of 3,5/2/1,5. I have found some organic fertilizers by BioBizz that are in my budget for the next grow and flo of this grow so I will be switching to them very soon. Manure isn't really good as I found out. Also, the soil I used isn't really good for weed as well. However, I think that the plant was nutrient deficient because it was overwatered for so long. I had small leaves with weird colours for a long time and I thought that it was normal, but from the time I stopped watering I see very large and nice green leaves and stems, you can see that in the photo. But I much appreciate your comment. Thank you and good luck with your growing :)