Senescence is when plants will naturally yellow off and die. During the final weeks of flowering do not be alarmed. Leaf drop and yellowing always increases. Flushing plants with pure water or a flushing solution at the end of bloom will also rid the medium of residual nutrients and often causes...
Those 2 possibly getting more or Less water?
Seeing the watering rings, are you auto watering?
Is everything working properly,,,,Pump,Timers..Check everything.
Feel the weight of them compared to the other 2
Over Watered
Don't water for at least 3-4 days,Maybe more?
Definitely do not soak all the soil at this stage
Just let them dry out
And be very careful how much you water.
Remove the curled leaves from pic 4 :clap: