2002 Pontiac Grand Prix Fluid level on battery

l just had a Bosch car battery replaced less than a month ago. The fluid level on each of the six cells has gone down. I have added distilled water to each low cell. I'm currently not having trouble starting the car but I commute 1.5 hours to work each day and I need to have a reliable battery. Is this battery bad? Do I need to have the place I purchased the battery check it to see if it is being recharged? I don't believe it is my alternator as I had that replaced last December. I thought Bosch car batteries are known for their quality?

Thanks for your time.

Sincerely,

Steve Thiesen