I have two Maine coons just turned six months. Sometimes when they are eating or chewing something they make a sound like they are eating crunchy food - even when just eating wet food. I can't believe it is just their teeth grinding as it's a definite crunch sound. It's quite disconcerting. They have recently been to vets for checkup and he looked at their teeth and nothing amiss (though I didn't mention the crunching then). Any ideas how they are making that sound?