when a plant goes into flowering. Lower leafs will start to die off. But your plants have some funky looking fan leafs. What kind of lighting do you have? Do you have much ventilation. Does your grow medium have good drainage. I would not be worried about the lower leafs dieing off. but those funky fan leafs that look like spinache should be addressed. But then again, maybe i am not look at it correctly or something.
Fan leafs have long stems and also they only have 3 leafs per fan. Hmmmmmmm You sure you have enough light?