Megabytes boat is kept in full sun exposure. The boat left in the rack could be in shade, so the hardware sits wet and doesn't fully dry. Any standing water or condensation left to sit on 304SS will cause it to 'stain' what looks to be rust, as it is an oxide precipitate.
It can also mean the bedding on your hardware is compromised and needs to be replaced. When I took possession of my '92 hull in 2000, I removed ALL thru-bolted hardware (I wet out the wood core with thinned epoxy) was re-bedded in LifeCaulk (those subject to strain, e.g., cleats, hawse pipes, etc.) with everything else bedded in Life Seal, both products by BoatLife Company.
This is typically seen on the rear fifting eyes that 'weep' rust stains. My '92 shows no such staining ...