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If it's white and looks like "sugar crystals" it is plume, or bloom. Plume is harmless and normal. I've usually seen it as small white dots that wipe off easily, unlike fuzzy green mold that was on an ISOM I had improperly stashed for too long. That said, if you just bought it, your local shop should have no problem taking it back.
Mold can be white as well and when I used to run a cigar bar I saw more white mold on cigars then blue/green mold. You are not going to find "bloom" on cigars in a cigar shop as bloom will only develop over time (and lots of it) of the cigars sitting undisturbed and this typically does not happen in cigar shops. Bloom appears uniformly across the cigar and does not wipe off easily, if you can brush it off with a light touch, it's mold. Look at it under a magnifying glass and you can see the little spores growing.
Most shops over humidify cigars for 2 reasons...1 the humidors are opened many more times than the typical desktop and the shops want a "buffer" to help prevent the drop in RH. The other reason is that cigars in a shop are often mishandled and this can lead to damaged product. The more humidified they are the more "durable" the wrapper becomes to rough handling.