So, what are the collectors doing? Should I bother to have a theory about this? Probably not, but here we go.
So, remember when the scavenger said that everything in the ocean seems to drift away from everything else? The only way that makes sense is if the planet is expanding. (It's like blowing up a balloon with dots drawn on it. All the dots get farther away from each other.)
Put this together with the map with the slowly growing sphere, the break symbol, and the symbol for the elemental water plane, and bingo bango, whisky tango -- the collectors are flooding these planets with water from the elemental plane through the break, which is some kind of dimensional portal.
Maybe they're going to drain the planets once they've drowned everybody, or maybe they're just huge fans of Waterworld, which would be worse.
Any other theories?