What‘s the problem?

It looks to me like a potassium deficiency, which is pretty common around this time in flower since the buds are demanding more nutrients. The yellowing leaves and crispy brown edges are classic signs that the plant isn’t getting enough potassium to keep up with the bud growth. At seven weeks into flower, the plant’s nutrient needs are at their peak, so you might consider slightly increasing the potassium levels in your nutrient mix to help the plant finish strong. Double-checking your pH could also help ensure there’s no nutrient lockout making the issue worse. You probably won't see the damaged leaves recover at this point, but adjusting the potassium should help prevent things from getting worse and support bud development through to harvest.