That's the beauty of relativity, and why it is called relativity: it's all relative.
When you go fast, and look outside, it looks like it is the outside that is moving fast (unless you are experiencing acceleration, at which point General Relativity kicks in). Therefore, to you, it looks like time outside is moving slower.
When the space boats are doing their thing, to us on the outside it looks like they are moving fast. Therefore, to us, it looks like time for them is moving slower.