New batteries loosing charge after sitting a week.

There will always be phantom drains on the batteries unless power is disconnected at the batteries themselves.
Next thing is, were the batteries fully float charged before being put into service? Its difficult to say how long they may have set on the shelf discharging.

My routine before putting any battery into service is to bring it to a full charge. Use a hydrometer and check each cells spg. and equalize if needed.