what should i do?

Pull those yellow leaves as they are not useful anymore and just water them everyday but don't leave them in standing water let them drain and check your nuits or just buy multiple purpose nutrients that makes less work for you and don't let your soil/coco dry out to much only in late flower as the plant take oxygen in roots to firm up the bud I add that as I notice your medium looks very dry good luck and if you choose to change nuits training little by little is always the best 👌

Start a diary so we can help you. We don't know what your feed is. The temps, humidity, light distance, ph, ppm etc. We need these things to help you. So I recommend you utilize this platform for what it's for and start a thorough diary and re post your question.

Hard to say without a journal. The biggest 3 contributors to this yellowing usually are a bad environment, incorrect pH, or underfeeding. You want to water them with water at pH ~6.0-6.5. If you are not pH'ng your water or soil, you can easily run into nutrient lockout very quickly. As far as environment, make sure your VPD is close to 1 as possible for plant respiration health. If your VPD and pH are good, then you're probably not feeding them enough. It kinda looks like you're in coco but I can't tell for sure, if you are coco drains fast and requires the application of water/nutrients more often.