As an E30+ owner, the things I would check are as follows:
1) As Loren mentioned, the rudder stuffing box is often ignored. It is accessible through the port cockpit locker and there are several nuts at the stuffing box flange, which should be snug. Mine kept loosening, so I added lock nuts and that solved the problem. There are also 2 zerk fittings, one near the top of the rudder shaft (very hard to see) and one under the plate at the bottom of the shaft (also hard to find, but they are likely there). With a grease gun, add lots of grease to both fittings, being careful not to break the zerk fittings off as you remove the gun. If it is leaking water at the stuffing box, you should see it being a bit wet after a sail with the boat heeling.
2) Stuffing box leak is a possibility, but if you put a paper towel underneath it, or some white chalk, you should be able to see if it gets very wet while the boat is in it's slip. If so, tighten the stuffing box, or replace with a dripless shaft seal next time you haul the boat.
3) The keel on the E30+ does flex a bit during a hard sail, and water can enter the bilge if the keel/hull joint hasn't been recaulked or sealed properly. Rebedding the keel solved this on my boat--not a cheap job, but maybe necessary after all these years.
4) If I overfill the optional forward water tank (under the V-berth with the deck fill at the bow), I get a bit of water in the bilge for a day or two after. Similarly, if you have a leak in any of the fittings or inspection ports on either of your water tanks, or holding tank, that water will end up in the bilge.
5) If you have a leak in the connections under the galley sink, that water will also end up in the bilge.
If you have the E30+, as far as I know they are all deck stepped masts, so you should not have any water from the mast in your bilge.
With careful inspection of these various possibilities, I'm sure you can determine the cause. Good luck!
Frank