what do you thing is the cause of the yellow leave...

This phenomenon is called senescence and it's a pretty natural thing ! The plants are acheiving their cycle and they will "suck" the last nutrients from the soil & the leaves to bud fatter ! Some nutrients like GHE Ripen were created to encourage senescence at the end of a grow ! So if a nut were created to emulate what's naturaly happens with your plants , it's mean your plants are doing good ! I hope it will help you 😁👍

Hi @HappyGrower420! Your plant is ending its flowering stage and taking energy/nutrients from the leaves, she's telling you she'll be ready in a couple of days. She may have been under-watered also. I'd recommend to stop feeding now and start the flush, 4-7 days with TopMax and 4-7 days with only plain pH'd water. Hope this will help, keep us up-to-date and happy growing 👊