I have a Protank 2 Mini, (I think that's the name), on a Mini X9 and I've read on here about "washing" coils. Do you wash it with just water, when changing flavors? The water doesn't hurt it? Do you wash out the tank, too? I've just been adding the new flavor to whatever's left of the old. Also, how do you know when your coil has "gone out"? Salesman told me they last a couple of weeks, and I've had mine that long now. Just got some 1.8ohm replacements in the mail. Thanks.