2012 Mazda 3 2.5L Coolant Leak?

So, umm... my 2012 3 DD has a mysterious coolant leak. The expansion tank is going from the MAX fill line to the MIN line in about a week's time. It's definitely leaking onto the ground, because I see drips every once in a while.

The question is... are there any common places for these things to leak coolant? FYI... there's no temp gauge on the 2010+ Mazda 3, just idiot lights. I plan on pulling the undertray when I do my next oil change to look, but if there are any common areas to look out for, that would be good to know. Thanks dudes!

Mine does the same thing, it never goes below the min line though. I keep some in the back in case it does. I can't see where it is leaking from but I've seen a drop here and there in the snow.

rent and use a coolant system pressure tester from your local auto parts store and find the leak.