it's probably a bug.
there must be something that your HFS does and the maverick's one doesn't, that wastes memory.
There's no way for me to know what, from here.
What i would do if i was on your computer, to find the problem, is to disable whole parts of the thing, and watch the usage growing.
When the growing is took back to normality, then i would know i found the thing.
If the growing is fast enough, it would be easier to make this test.
Until we don't know what it is, it's hard for me to work on it.