Coco grow problem

Hi there. I also had a problem with burn symptoms similar to yours around the same stage, and I thought it was due to excess nutes, but it turned out to be because of unstable pH. Also, you always have to keep in mind that with autoflowering plants, the amounts of nutrients should be lower compared to photoperiod plants. So if you start with a good substrate, they have fewer nutrient needs, which are also directly proportional to the size of the plants and the amount of lumens from the light. Increases in nutrients should be as gradual as possible, and you should avoid drastic changes in fertilizers between different stages of development. Then, without a doubt, if the pH is too low, especially in hydro or coco, deficiencies can manifest very quickly due to nutrient lockout in the leaf system. Monitor the pH and keep it in the right range; if the symptom persists, consider other possibilities for deficiencies or excesses. I hope you can resolve it soon. Happy growing! Cheers!