If it's just the bottom leaves, don't worry it's natural. The leaves will shed or you can cut them off with clean snipers and dust the cut with cinnamon.
If it's upper leaves - are they still plump? Most probably due to too much sunlight. Move the plant out of direct sun or to an East facing window (try to keep it pointing the same way though in relation to the new light source or the flower stem will twist)
If it's upper leaves and they're soft and wrinkled then you're probably under watering. Plunge the pot into a bucket of water once a week, until the bubbles stop, allow the pot to drain and then stand on a tray of gravel.