Does anyone know what nutrient problem this could be?

you are close to harvest, so forget all problems in leaf colour, too late to correct or stress about anything else than harvest ;) call it natural fade, autumn fade ;) no weeks in diary, on last 4th they looked hungry, here maybe nitrogen excess and small calcium issue, but as i said, could be just finishing plant .. have fun harvesting ! lsd is tasty strain , enjoy !

i don't know.. looks like a fairly typical biobizz canopy to me. do you just give 1L each day? This may be oka, but if you picked the number out of the ether, the chances are more likely it's not quite right. always water entire things. if soil, minimize runoff and soilless a religious 10% runoff waste every time no excuses. you want for top portion to dry relative to water holding capacity of the pot and repeat. You don't pick how much water is needed. you give as much needed to get the job done. This sounds like no big deal, but over time the blind, whimsical way of watering leads to problems.. buildups, pH issues, superficial roots, which if you have any erosion/compaction, which happens over the course of 3-4 months of growing, whill expose those superficial roots to light and then they become useless stems loosely covered in dirt, which is a net-negtive for nutrient uptake, obviously. I bet this is from an imbalance in the biobizz instructions as well as bad watering habits. you'd have to be honest with yourself with the latter to verify. If you didn't have good watering habits this is almost certainly some sort of nute or ph lockout. it's already in the plant. it would take a long time to correct it.

your so close to harvest, they wont die before there job is done. Bud looking so dense, i would just take it

Potassium is mobile in the plant and I would have thought all mobile deficiencies start at the bottom of the plant first. Wondering if it might be something else as some of the yellowing is on leaves with a green edge and that's not typical of potassium it gets the edges first. It is looking extra rich in N from the pictures. and when the tips curling in on them selves make me think overfeeding. Its so close to harvest I don't think I'd worry or care that much about it tough. plants look great should be a nice harvest. Always ensure you getting proper runoff when using liquid nutrients or it can get buildup in the medium that mimics a lot of deficiencies. Still good work on your first grow. Good Luck!

It appearance to be potassium deficiency. I woukd not worry about it. You ate at the end and all she needs is just water as she ripens. Adding nutrition in final week or two can give the flower a bitter taste.

It looks like it’s a possible potassium def though.

It’s possible that she is a bit hungrier than what you are feeding. So when a plant gets hungry it tends to eat the fan leaves to keep producing buds. Honestly you’re so close to end right now that I would just keep doing what you’re doing and don’t start overthinking it. The buds are there and they look beautiful and they’re not going to spontaneously disappear. At the end of the day buds are the prize. Not fan leaves. Honestly just ride it. I’ve had the same issues in late flowering and the buds still turned out to be great.