Decomposition of Esters in Old Scented Markers

We have some old scented markers in our Sunday school classroom and I have noticed that in addition to the pleasant fruity and minty smells I noticed that there is a sort of a vinegary smell.  I assume that is due to the esters that produce the scent decomposing to produce carboxylic acids such as acetic acid.  Our department chair has pointed out to me that when he opens a bottle of uncoated aspirin he can briefly smell acetic acid, presumably from decomposition of that ester.