Also, as Rob somehow implies, I would not advise to hunt for memory leaks and instead, while developing, just place a memory usage counter on top of everything that monitors constantly, and only tackle issues when a very specific problem arises.
The same for releasing texture memory, by the way: in my latest game, instead of cleaning up every imageSheet after use (and then needing to reload it again later on) I find it’s easier to just keep them in memory.