How long was it? 1% per day sounds normal if it's just for 2-3 days (probably a calibration issue or drains while turning off-on, which is no big deal).
If it's two months and it's down to ~30%, then something is probably draining it just a little and preventing the tablet to be completely off. What's the OS on this tablet?
Note that the best way to store (connected) battery inside a device that's turned off is about 50% charge. This is why when you bought a new device and turn it on it's usually around 50%.