Yes the valves could be too tight allowing loss of compression. So could bad rings, or a blown head gasket. If a valve was too tight for too long it could be burnt.
Check your valve lash and adjust if needed. If still low, squirt a little oil in the spark plug hole and check compression again. If it goes up, it could be your rings. The oil helps them seal a little better temporarily for the test.
Crank it over with the spark plug out and see if any water blows out to check the head gasket. Is the oil milky? Any white exhaust smoke? Condensation on fill cap?
Not sure what else you checked. Just throwing ideas out there. Good luck, hope it's just a tight valve.
