Saltwater is a killer for metal so it's not suprising that the gas springs are rusting away after 6 years.
They flake rust which left orange muck all over the nice white gelcoat. They had to go!
I found a really helpful seller on eBay.com called "buds1946" who shipped me two replacements to the UK at a very reasonable price.
(You will need to log-in to see the pictures)
The 12" SPD Black Nitride GSNI-5100-40 in the swim platform locker was replaced with a 12" Stainless GSSX-5100-30 (10lbs less pressure but lifts perfectly so doesn't make any difference)