Fruit Gelato Auto

Today,13th May, they are in day 78,starting of week 12 from sprouting. They are Fruit Gelato Auto from SeedsMafia. Until day 50 they haven't started to flower so in day 50 i flipped them to 12/12 schedule. On day 60 they started to flower so in this case i assumed they are actually photoperiods. Yesterday,12th May i have heave defoliated the tallest plant on bottom and middle of it because she shown yellowing leaves with brown spots on them as you can see in the pictures. I don't know if that yellowing was normal because of the maturity of the plant or there is a nutrition deficieny. It's my first grow and i didn't know how to create a diary so i'm very sorry about that. I'm new to everything related to this hobby.