Cracking up...

First it was a weird crack in the corner of a window,
then a wine glass
then a mirror
then another two wine glasses
then the fish tank( which caused a major panic as it's an 80 litre tank!)
then a tumbler
then another wine glass

...nothing for a while,

then I found this in a cupboard yesterday. It definitely wasn't cracked when I put it in. In fact all of these glass things cracked without any external force that I'm aware of. Could be some weird sound frequencies bouncing about my house but I don't know.

Am beginning to get very freaked out now.