Why do patterns appear on tempered chocolate?
What you're seeing is called chocolate bloom. It doesn't happen because of tempering, it happens in spite of it (or sometimes due to improper tempering).

Sugar bloom is pretty straightforward - it happens due to moisture exposure (e.g. condensation) causing dissolution and re-crystalizing of the sugar on top. You can easily check if you have sugar bloom by wetting your finger (just a bit!) and wiping the grainy/streaky surface. If it becomes smooth after doing so, then you got sugar bloom.

The other type, fat bloom, is more complicated, but ultimately it boils down to having different types of crystals (and specifically crystals that are not the beta crystals you want from tempering). It can happen for a lot of different reasons, but some of the most common ones are:


Not heating enough before tempering. You might have melted most of the original chocolate but not quite all of it.
Too much heat in the 3rd stage - if you melt some of the beta crystals, they can form larger crystals and push cocoa butter to the top when they re-crystallize. This happens to me every so often when I decide to make a way larger batch of chocolate-coated whatevers than I really have time for, start rushing near the end, and heat too much/too quickly in order to keep it melted.
Fat migration, due to incompatible fats on the surface of whatever you're coating (maybe nuts, or something with oil or butter) mixing with the melted chocolate. This is more likely to happen later in the process, after you've dipped and coated a whole bunch of them, so it's probably not what happened to you here. Also, it's more likely to happen when the coated items are at a very different temperature from the chocolate.
Cooling too fast during or after molding. I don't know the scientific explanation for this one, but it's pretty easy to demonstrate by throwing enrobed chocolate into the fridge right away - it almost always blooms. This can also happen in more subtle ways, e.g. if a nearby air conditioner happened to be running while you were working.


Unfortunately it's almost impossible to tell which specific problem occurred simply from looking at the end result. If it's any consolation, though, I don't think yours really turned out so badly compared to what can happen with bad tempering.