Typically once silicone sealant becomes dark in color nothing will clean it except replacing it. Mine is starting to darken and will be redone this spring. To keep it from happening is tough, it has more to do with the sealant and its ingrediants then anything you can do. Keeping the deck dry and clean helps but will not stop it, it is typically caused by the sun actually. There is a difference between mold itself and this discoloring of the sealant. Your best bet is to complain to grady, they will often send you new sealant to match your color to keep customers happy, I have not called yet so we will see if they are as accomodating as usual with the slower times, hopefully they are. As for the hooks, unless they are Stainless steel they will rust over time. They do better if rinsed with fresh water and then allowed to dry and then put away out of the salt air. If you leave them outside in the salt air they will not last long. I do not expect my hooks to last a long time anyways when fishing for inshore species and plan for this...I tie about 150-200 fluke rigs and 150 or so striper rigs for the season to get me through our 40 or so trips we make. I usually can use my hooks about 5 or so trips if they are a duration metal finish, and a few more if they are a black finish like a gamakatsu or owner hook. Once the hook point rusts and looses it sharpness you can resharpen it for maybe one more use but then throw it away. I buy hooks in bulk to save money and tie my own rigs, much cheaper then store bought rigs.
Not much you can do with the hooks except try to make sure they are dry before you put them away. I usually just throw the rusted ones away - its not worth the effort to try to clean them up.