Some water loss is inevitable, so you do have to add water once in a while. An inch in a week? Not outrageous. There's a lot of evaporative loss whenever the cover is off. And you have a pretty large number of users - each of whome takes some water out of the tub when they exit.
Do check for leaks (I would do this on a new tub no matter what - yours wouldn't be the first new tub with a leak), and also - very important - make sure your cover is sealing well. Check the center seam also - nothing should be getting through there. You should feel a bit of suction when you go to remove the cover, which indicates a good seal to the shell. If all looks fine, I don't think you have a problem.
Thanks for the ideas and for letting me know that an inch a week doesn't sound outrageous. Our tub is a used one, the cover is new, but I don't feel a suction when I go to remove the cover. The person we bought the tub from ordered the cover for us. The cover is bigger than the hot tub. Is that an issue? I have no idea what is normal. I did look for water today at the base of the tub and didn't see any. Help with ideas on my cover would be great. Thanks!