First kush grow

Hi @FrostyBuds! Not sure about the wind-burn, it's hard to say with the 2 pictures you provided, but about the brown spots onto your leaves yes they are showing signs of a Phosphorous deficiency OR pH fluctuations. Since you've been giving only 1.3ml/L of nutrients, I disagree with the other answers : yes you're having a nutrients lockout, but no it's not from too much nutrients. It's - in my opinion - because of overwatering. Your pots look verrrry wet and your substrate's color make me think you drowned your roots. As an emergency move, I'd try to let the soil dry for a few days : your soil needs to be on a dry/wet cycle otherwise roots won't spread and search for water. Compact soil or over-watering can lead to a Phosphorus deficiency, even when all other parameters are perfect. Once the soil is almost 100% dry, transplant in a bigger container with fresh soil and give it a good meal with the correct pH range (~6.2). The bigger pot will help roots to spread and will prevent from root-bound & under-watering. Also, you may want to re-calibrate your pH-meter, to ensure your issue is not coming from wrong pH and/or pH fluctuations. Then see how it goes. Hope this helps, I'll be around, keep us up-to-date so we can help you adjusting your parameters, and happy growing! 👊