Fan leaves falling off

During flower is it normal for the fan leaves in the middle and bottom to wilter and die. Som don't even wilter they look like healthy leaves. I had a bad cal mag problem that I'm fixing now could that be the problem or is it normal? I have 12 plants and I loose about 10 to 15 leaves a day.

10 to 15 leaves from one plant or a total from 12 plants?
how old are they into flowering?

have any pictures.

That's not normal at all. Throw a picture up here is you want some type of diagnosis, and give us your growing conditions.