The joys of DB I would say dont change the strings unless you are buying it so start with the adjustable bridge. The string wont of got lower unless the tuning has dropped by quite a bit, is it in tune? If it is could the front of the bass or neck be unstable? If you are going to adjust the bridge I would say two things from my own limited experience so far, put some masking tape to mark exactly where the bridge is before loosening the string tension, it is amazing how easy it is to move it without getting it to seat correctly afterwards! the second thing would be dont remove the strings at all just loosen them enough so as you can raise the bridge, at least if it does fall to bits you will have the marks for the feet and the strings under some tension enough to stand it up and get it roughly in one piece
I'm not sure if its right or not but as a rough guide reading other threads I have got mine set with 7.5mm from the underside of the G string to the fingerboard at the end of the fingerboard, rises up to 10mm for the E string roughly. I am tempted to take them all a tad lower but I have the opposite problem in as much as I need to remove a bit of the bridge as my adjusters are right down, I wanted to wait until I was sure the wood has settled as it is a brand new Gedo bass.