when I see the tips all brown like that I thought nute burn, but because the leaves are curling Im gonna call it a zinc deficiency. possible phospuros deficence also. cant help more then that as I don't use dirt. it could also be a toxic salt buildup. I would flush first then talk to others that grow in dirt and see if your using good stuff. I use hydro nutes and push the limits and usually do get a minor minor case of nute burn, but I take it as a good sign that I am right at that overdose limit. when I say minor I mean like a couple of leaf tips burning.