What did I do to make the chocolate bloom like this?
My best guess is that the chocolate was too hot.  It may have worked on your test because it was small and thin, and therefore cooled quickly.  In the larger molds, it stayed too warm and you got the wrong kind of crystals from the cocoa butter.

You want the keep the chocolate as close to 88 °F (~ 32 °C) as you can get.  What I typically do is microwave 3/4 of the chocolate at 50% power until it's pretty much melted (just a few stubborn bits remaining), then add the other 1/4 of the chocolate and stir to melt.  Sometimes it has to go back in the microwave to completely melt the last 1/4, but only about 5 seconds at a time.  Very short bursts.