2nd week of flowering= leaves falling off

I'm in my second, almost 3rd week of flowering and some of my lower leaves are starting to turn yellow and fall off can any one tell me why this is? the rest of the plant is healthy as a mother fuck

nitrogen def.
The plant still needs it.
what are you feeding? what soil? hydro?

Like smiley face says, It's lacking a bit of Nitrogen (N)

Also, When aplants begins to flower it often 'cuts dead weight' by disgarding a few bottom leaves that have 0 access to light to concentrate energy on buds/upper leaves.

What medium and nutrients are u using? EC?

I'm using miracle grow as a medium and I just picked up some foxfarm big bloom today. Aren't coffee grounds high in nitrogen?