Tires always lose air in storage is this normal?

I would not recommend tubes in a tubeless tire.

You may find it will cause more problems than it will solve and possibly void the tire warranty.

As for pressure loss temperature is a big factor. If temperature is the same before and after storage things do not add up. If it were only one tire I would be looking for the leak but you indicate all the tires are involved. As such I doubt there is a leak problem.