That’s what we call bloom - if it is crispy to touch it’s sugar bloom, if oily it’s fat bloom.

Sugar bloom is usually the result of leaving chocolate in the refrigerator then when you take it out condensation forms on the surface.  The sugar in the chocolate dissolves in the condensed water and as the water evaporates, the sugar comes out of solution, resulting in crystals on the surface of the chocolate.

Fat bloom can result from poor temper or a fatty center that is leaking oil through the shell.

No! Once your chocolate is in temper you have dissolved the unstable crystals and you have a predominance of stable beta crystals in your chocolate. As your chocolate cools, it will become thicker as the beta crystals grow and multiply. As it thickens you can warm it again either by heating with the heat gun or microwave, or by adding warm untempered chocolate. The beta crystals in the tempered chocolate will act as a seed to temper the newly added untempered chocolate. 

You will find if you have been working for many hours with your tempered chocolate that it seems much thicker at the same temperature than it was before. This is due to the multiplication of stable beta crystals. You will be able at this point to heat it a degree or two higher than the standard working temperature in order to make it thin enough to work, without driving off all the beta crystals. Just be careful that you don't exceed about 34 degrees for dark chocolate, 32 degrees for milk chocolate and about 31 degrees for white chocolate. 

Tempering is the process by which stable cocoa butter crystals are formed. This gives us chocolate that shines and has the snap when we break it that we associate with fine chocolate. Tempering also allows chocolate to shrink as it cools and that allows chocolate molding, releasing from the mold as it cools.

As chocolate cools down to the tempering temperature wild crystallization occurs. Alpha, gamma, beta prime, beta double prime and beta crystals all form. Only the beta form is stable. As we heat the chocolate to the working temperature, we melt first the alpha, then the gamma, beta double prime, beta prime and leave only the stable beta crystals. If we over heat at this point we dissolve all the beta crystals and will have to do something to reintroduce the beta crystals we require.