How much longer would you let her go before cutting!?

26th March

Not light burn, something long term wrong with the soil pH or feeding schedule. Plant is "unfixable" at this late stage, however maturation will take longer due to the damaged leaves being inefficient. I would still give her another 5-7 days, maybe even 10. Once there are 98-99% brown pistils/hairs, you will be in the harvest zone. Reducing the lights on time by one hour may make her hurry up and finish.

If they had a burn it will get a bit worse, since parts died and the necrotic spreads a bit. But mostly plants have some issues with the leaves if they go into late flowering. Their lifecycle is mostly over and they start to mobilize nutrients from the leaves into buds.

It looks like the bottom calyxes all turned brown allready, that means you already missed the maximum potenc eharvest window. Top buds are a bad indicator, since they are younger. If you check the trichomes, also on top they are probably already amber and milky. Then i would harvest right now But its hard to tell via pictures. If the bottom calyxes arent completly borwn yet, you still have some time. But I would rather check closely and decide on the trichomes

More than a burn it looks like a potassium deficiency to me