I've never heard of any bow being mismarked by 25# regardless of it's age. Are you certain you're reading things right.
Regardless, hitting stuff hard will not bulge a cedar shaft, well maybe right behind the head as the head is pushed further onto the shaft a shot or two before it breaks there.
There is a compression tool available that some folks may have used on the arrows in question. It's a steel block with a tapered hole in it. It's heated and the shaft is chucked in a drill and spun through the block, compressing the outside fibers of the shaft such that what goes in as a 23/64 comes out as an 11/32, or a 11/32 to a 5/16. If the person doing the spinning doesn't maintain an even thrust on the shaft, it can overheat in that area and cause a discolored ring that may look like a bulge. And, in fact, there may be a bulge in that area because the extra/extreme heat might have overcompressed that area relative to the surrounding area. The compression may also create bulges if the shaft is pushed through fast, but eratically, with stops and starts in the forward progress.
The same thing can show up on arrows directly from the factory, without compression ever being involved. Just poor finishing due to dull, out of alignement burnishing/sanding machines. Burnishing and sanding are the last steps in the shaft-making process.
Difficult to say where in the manufacturing process the bulges were left in or created in your shafts, but they weren't created from shooting into hard targets. Cedar will break rather than bulge.