 Probably not. I think what you're seeing is this. You have warm, moist air that's going to be collecting at the bottom of that refrigerator, and that moisture is going to be enough to feed the mold. If you're wondering why is mold forming there, it's because mold will grow on dust, and it's also an area where you get a lot of dust that sticks to the bottom of the refrigerator and sticks to the baseboard. So if you had the dust, which is sort of the mold food, and you had the moisture, that's what's going on there. You don't necessarily need to have a leak there.