My humidor looks like the one below, the only differrence is it has 1 smaller piece of glass on each side of the hygrometer. for some reason i can not keep it at higher than 60% I believe it has a leak that is keeping it from keeping any more humidity. I have tried several different options short of getting ready to buy a Cigar Oasis just to maintain. My question is if I wanted to add some sealer to the edge of the glass where, and what type should i use?

Should I
A. Use the kind for plumbing and put it on the inside
B. put it around the out side, this would really make the humidor look bad
C. Use something like candle wax??

Just not sure what I should use and where it should go