The only thing Iknow that causes this is washing in a dishwasher. Most crystalware is not dishwasher proof. If this is the cause, the "bloom" is actually damage, like micro-scratches, on the glass. If, on the other hand, it's a bloom caused by something like hard water, then try soaking in vinegar or solution of washing soda, and polishing with a microfibre cloth.
aliceM, October 2009