Plumbing, rig, batteries, tankage, the head itself, tool stowage, anchor in well off center, mast not vertical, keel not perfectly plumb and level--or even lopsided after fairing. Could be any of those things and even the hull layup may not have been perfectly symmetrical, boats have been known to carry trim ballast to correct these problems.
I'd agree with the others, check everything from stem to stern to look for things you can shift to trim the boat, and double-check the level itself. From a dingy (so your weight isn't a factor) or the dock, measure from the deck to the waterline and see if the boat is really heeled by that measure. And you can check for a plumb mast by taking a halyard straight down to the deck at the rail/chainplate, and measuring to see if the length is the same to both sides. Or, measure with that same halyard to the water.
No big deal if you have to add trim ballast, but if you don't need it...lighter is faster.