Why are the leaves tips curling dying and brown marks appearing?

it looks like a combination of a few things. chlorine toxicity. calcium deficiency. and lack of nitrogen which can happen late in flower naturally but it doesnt look like a normal fade. are you using dechlorinated water? my best guess is thatits a ph issue and the plants arent uptaking as well as they could. also looks like you may be pushing nutrients too hard. ill take a look at the whole diary and then send you a message with anything possibly helpful. i need more info than just the pictures. buds look great overall tho. best of luck 🤙