Thanks for posting details, Audrey. This information is more valuable than you know. When it comes to figuring out how to get a particular species to breed, information like this is really all we have to go on.
There has been some speculation with other species that sunlight or day length can be a stimulus for breeding. So it's quite possible that a bright room had some effect. I also think that, although you haven't gone out of your way to vary the temperature, it's undoubtedly warmer in summer than in winter, and even a small, consistent shift like this is enough for many species to decide to breed.