Can't figure that, how could all 6 cylinders lose compression at the same time ?
Are you sure that the cams are also turning along with the cam sprockets ?
All I can think of offhand is a slipped cam drive gear on the crankshaft .....
This is an INTERFERENCE engine, be careful !
If the cam/crankshaft timing is too far off, you could be seeing bent valves and banged up pistons.
( This could have already happened, but you should have noticed that, it is not a quiet event ! )