Cymbidium falling buds and yellow leave

[master_xelis]

A month ago I bought a Cymbidium with a flower spike with some buds. Some days ago I noticed that a bug was eating the flower spike and it was damaged because of it.
Today in the morning I noticed that two of its leaves were going yellow with dark spots and two of the buds of the spike were in the ground. They falled down!
Here where I live (Mexico) temperature has been low (about 14° C in the day and 6° C in the night with constant raining), with the exception of the last week, in which there was a heater temperature. That is the reason I haven't watered the Cymbidium since I bought it (yesterday night it rained).
It has been in a place with shadow since it was the way it was where I bought it.
Can you help me in order to not to lose the blooming?
Who knows the reason of the change of the color of the leaves?
Photos are below: