It might be sensitive to the chlorine in the tap water, especially since it has been used to purified water. You could let the water sit out overnight to dissipate the chlorine and see if that helps. I noticed a plant in a friend's office and he said the secret to his thriving plant was distilled water. Haven't tried that myself but it might be worth it to just keep watering with the bottled water.

I've heard the same thing about chlorine causing brown tips on spider plants.

I use regular tap water and my plants have done great for several years now. Sure, the very tips (say, the 1/4 inch at the tip) get a little brown, but it doesn't really detract that much from the plant, so I still use tap water for convenience. Some friends of mine trim the ends of the leaves off (to a point, use scissors at an angle to a blunt-end leaf doesn't stand out visually) but I just use tap water and still have good looking plants.

Let us know if you switch to distilled, or non-chlorinated or what. I do love spider plants as they're so green, and durable, and they don't mind if I have to leave town for a week or ten days.

Take care,
Grant