The effect of bad valve rubbers is not reported often. Yet there are a few cases where the poster stated his diesel smoking at startup was improved by changing them.

At the same time remember some have changed them with no apparent difference. Drop you oil level to mid way between the marks and see what happens first. You could be splashing so much oil on the walls the rings will not scrape down enough with a high oil level.

Are you sure the smoke is blue? An injector leaking down at rest will cause some smoke on startup but that should be blackish I believe.