So you used to sugar prime your kegs and things were fine or are you knew to kegging all together? If you had no issues before when sugar priming your kegs, I would certainly suspect a leak at your regulator, manifolds, fittings, connections, disconnects...etc. I used to burn a lot of co2, it would be every few kegs. Never exactly pin pointed the leak(s) but ended up replacing all my o rings, small and large and tightened every connection along the way. Now it seems I get a refill once a year.
If you do suspect your kegs, crank up the pressure and fill an empty keg, say 30 psi. Disconnect it, spray it down to check for leaks and leave it, try adding some co2 later and see where you are at. Go though all the kegs, but I suspect a leak somewhere else. By chance are they Pin Lock kegs? I had a disconnect on my Pin Lock that would fit lose, if it had and side pull tension on it, it would hiss and leak co2. I got rid of my 2 Pin Locks, went all ball lock.