Rock and a hard place. 12YB's v 2YB's. Vaccinate now or wait for 4 weeks until the two are ready? A lot depends on your own management. If you vaccinate now when the two hatch your YB's will only be a week through the process. I wouldn't think that would cause any problems, but I'm not a vet. If you leave it for 4 weeks, your twelve will be relying on their own immunity. Do you suffer from YBS, etc? Only you can make the judgement call. The OB's don't need done, again my opinion.