My lemon-lime has suddenly been developing yellow leaves. Do you guys have any idea what might be going on?

It lives in my shower, hanging in a south-facing window. Miracle grow potting soil for substrate. Water when close to dry but still barely damp.

It just recently went through a few weeks of flowering, sent out maybe 7 or 8 different inflorescences. I have no idea if that affects the plant....?

My initial thought is that it's too cold -- I live in Montana, and my bathroom is chilly. We get plenty of sunshine in the winter, so I don't think it would be too little sun, but maybe reflection from the snow is making it TOO bright? My red maranta had one yellow leaf a few weeks ago and it hangs on the other side of the shower curtain, so maybe?

If it is the cold, is it better to take the plant somewhere warmer but much drier because of the heater?

Please note photos were taken at night, so the plant doesn't look particularly perky at the moment.