I agree with removing some of the rear chamber media and rinsing the rest.
I don't think you want too drastic a drop too quickly so that's why I wouldn't remove it all.
To clean the media I would put it in a bucket, with a little tank water, then turn your return pump off. Scrape inside your filter and return sections as much as you can, wipe down your skimmer heater etc, and then suck all of the water change out of the back chambers thus removing as much buildup as possible.
Put your fresh salt water in and test again in 2 or 3 days.
I don't think you want too drastic a drop too quickly so that's why I wouldn't remove it all.
To clean the media I would put it in a bucket, with a little tank water, then turn your return pump off. Scrape inside your filter and return sections as much as you can, wipe down your skimmer heater etc, and then suck all of the water change out of the back chambers thus removing as much buildup as possible.
Put your fresh salt water in and test again in 2 or 3 days.