I'm currently using the Shure SE535 with the black Olive tip. The medium black olive tip now fits my ear perfectly while it was a little too big at first.
Can tips make your earholes bigger?
Doubt it... I think the foam tip compressed a bit ;) tips change size and shape with use. It's possible that your ear is bigger, but more probable that the tip has changed.
It might just be a psychological thing.
You might not have tried them properly when you first got them.
But then again it's not impossible that your ears change over time (might not be from the tips), I've heard people having to remold their custom in ears after a while.