For some reason, I've noticed lately that the soil of my African violets seems to be freezing. I don't know why. It feels like someone has been watering them with ice cubes on purpose (though there's no sign of watering from someone else being done)!

They're in my kitchen window, so they get plenty of sun and it never gets too cold in there. I give them warm/room temperature water when the soil feels dry.

In this situation, the soil is wet and cold. Yesterday, I fixed it by giving my violets the tiniest little bit of warm water, so their soil would warm up. But they're cold again, and I don't want to over water them.

Is this normal? Does this sort of stuff... Happen? Or is it more likely that someone in my household would be giving them cold water on purpose (but again - no signs of watering done by someone else. I asked the others too and they "swear" they didn't do anything)?

Edit: I forgot to ask - what can I do to prevent this from happening again, and to fix it?