I've hunted lots in salt water environment, and when using blued firearms always fought losing battle with rust, even with daily maintenance. But I don't know if your problem is actually rust. Despite having 2 Glocks I'm not at all as enthusiastic about them as you are, although for a "carry" gun Glocks and some other polymer pistols can be desirable, and it's a pretty solid choice for your purposes.
My Glocks get shot lots, and light strikes can be an issue after a few thousand rounds so replacing the recoil spring can help. I don't know how much yours gets shot but I would put in a new recoil and striker spring in at the start of the season and possibly look at a Wolf Extra Power Spring. When the recoil spring gets tired, it can cause the firearm to not go fully back into battery and you will get a "click" instead of a bang. There is a simple test for checking this.
WD40 can be great but it can also get gummy. And if some of it is getting down your striker pin channel (which is supposed to be dry and free of lubricant) then that could be causing a problem. G96 is what I would be using, despite the tests.
If your springs are new and functioning properly, I suggest you pop off the slide every day which takes about 30 seconds and check to make sure everything is moving, but don't load up the slide internals with WD40. Then I would shoot a couple of rounds every day to make sure things are working. I know, you aren't supposed to do that, so maybe dry fire with some primed cases instead.
Also, I'm assuming these are factory rounds and not handloads, which could be one other thing to look at.