I have noticed the same thing happening to my orchids as well and this surge in growth coincides with the hot rainy monsoon period in our area. I believe this is the natural cycle of growth in the areas where most of our orchids are found. From mid-Nov to around March will be the cooler dry season (winter?)in the monsoon lands and the time when most vegetative growth has stopped, and for the deciduous types (certain dendrobiums) to shed their leaves. This is the 'dormant' period in preparation for the 'spring' blooms.