Hi mate I’m no expert but I’m thinking it’s a potassium deficiency you have. Sometimes you’ll get something that looks a lot like tip burn with a potassium deficiency, but it goes in further than nutrient burn, and with a potassium deficiency you also see yellowing between the leaf margins (on a few pictures you can start to see this) Sometimes the first symptoms of a cannabis potassium deficiency look a lot like nutrient burn. One difference is the edges of the leaves will also start turning brown, where nutrient burn usually only affects the tips. And unlike with nutrient burn the leaves of a potassium deficiency turn yellow in the margins, especially near the burn edges. Hopefully this helps you out mate
