whats wrong?

what's up everybody, this is my second grow and i seem to have a little problem with my plant, and i was wondering if someone could help me out. it just started its second week of flowering and just about three days ago all the fan leaves changed from their healthy green color to a bright yellow. i haven't given it any nutrients yet, could this be the problem? its in fox farm ocean forest soil and i've been watering it with reversed osmosis water every other day. here's some pictures.

I would say it's due to lack of nutes. Your plant is now taking them from the fan leaves to develop the buds....Get her some nutes...