Take the plant out of the pot and examine the root-ball/potting soil. Is the soil saturated with water? If the soil is very wet, even "mushy-wet", you have a watering problem. Be sure the soil is extremely well-draining and that the water-saucer does not retain water after you water/fertilize. Always empty that saucer. Is the plant root-bound?
Regardless, it is time to change out your potting soil. IF the plant is root-bound, you'll need a slightly larger pot, perhaps 2-3" wider/deeper. Also, make sure that you water twice between fertilization, so that the salts from the fertilizer won't build up. I like to water my houseplants frequently, but I dilute the fertilizer by 1/2. If the fertilizer rate is 1 tsp. per gallon, I use 1/2 tsp. Fertilize weakly, weekly. I always amend my potting soil (in fact, I custom-make all of mine). Bagged potting soil is OK but I would add a cup of coarse perlite to every 4 qt. and/or add a couple of handfuls of orchid mix to every 4 qt. for better draining.
This plant typically will do fine in reduced-light environments, so I don't think this is a light problem. I also wouldn't think it is a cold/draft problem, since the plant apparently has done well where it is. But do keep in mind that this is a tropical plant and does best when it has good indirect light and mild temperatures, preferably above 50 F.
