Leaf discoloration

Hello dear growers, Thank you all for your answers. I'll try to give you more information. About the nutes, fan and lights, I added the pictures with more info. I dont think that I have a problem with a wind burn as the fan that I am using is really small, gentle and not so close to the plant. I dont suspect a root rot, as the discoloration on the leaves (symptoms) are there for quite few days and not spreading to the new leaves. So my gues would be pH too low as I am trying to vary between 5.8 and 6.3, I'll try to raise that to 6.3 - 7. Also as @Organoman recomended, I am going to cut on the nutes, I dont think that I was adding them too often, but maybe too much. On the side note, I was looking on different problems/symptoms with the plant on the internet, and the closest that I fount to my problem was a Copper defficiency most likely caused by wrong pH range. So I just ordered a propper pH meter as I was using just the test strips, and also I ordered a range of BioBizz food so I can be more confident about the nutes for my green darling. Thank you all for your shared knowledge, much uppreciated!

Side note, a PH of 6 is a bit low for a soil grow. You want to aim for aorund 6.4-6.8 and if your nutrients are dry amendments then even more so. This low PH is probably not helping the situation but I don't think is the direct cause of your issues. There is no fan in the cabinet for windburn to occur that I can see. I don't think that is the cause either. To me if it was root rot you would be seeing the damage systematically not just on top new growth. Manifesting its self like a overwatered plant with no oxygen to the roots. wilted twisted growth and mutated looking. We need the brand and ingredients or labels of the feed your giving them. Try uploading that into your diary. If you need any other help hit up your DM's Your inbox is the little green arrow on the bottom right hand corner of the screen. Good Luck!

The edges are fine that's sign shes loving your nutrient dosage. As for the edges this looks like windburn. Or rule of thumb(( never spray anything onto your plant when the lights are on)! I'm interested what kind of fan your using because that looks like some early wind burn !!

If it were potassium, which does start like that you'll also see brown following quickly behind the green and it'd be more along. Cause unless you took out a nute or added something to block potassium uptake your plant would of shown signs much earlier but root rot can take time to happen and happens more often in the latter stages of growth, as the roots are choking each other. Add micro and a nute that deals with root rot. Still very early to fix and if it is potassium all of what I said to do will not affect your plant. But if it is root rot and not potassium if it gets to far ahead it'll be too late. Good luck.

You could be running into a real problem. I think it's early stages of root rot. As your plant is getting the right nutes and uptake but early signs off root rot show the very signs u are talking about and your growing in soil. Maybe less water and look into a nute that break down root rot like tarantula good luck..

It looks like it is wanting some potassium. Your grow is looking impressive using 13W no idea of the NPK ratio or feed strengths your using may want to add that into the diary. They look like they do not need any more nitrogen though. Best Of Luck!