Take a photo of the lower mast inside the cabin, particularly where it meets the hull. On some boats there's often a block of wood under the base that compresses with age.
In your photos, it looks like you have a tabernacle that may have been added to your boat to make it easier to step the mast. Without one, you have to balance the mast vertically, drop it down through the hole in the top of the cabin, and align it with the base on the hole, all the while balancing yourself and hoping you don't fall off the boat! My DaySailer II was like that. After stepping the mast one time, I bought the tabernacle to avoid ever having to do that again. Anyway, it's a DIY project to add the tabernacle. You make two cuts on the mast, add the tabernacle in between, and secure them in place with tapped bolts. If this is the case on your boat, it's possible that one of the POs cut too much of the mast when installing it, which in turn causes your shrouds to be too long.