kindly visit your nearest doctor as it need clinical evaluation

Cracks usually appear if bridge is overloaded or may be some point in higher than other teeth.has to be checked for it.

Has to evaluated. In some cases repair can be done in mouth without removing the bridge. But first the reason for the crack has to be checked.

Roughly speaking, it is not possible to correct those cracks in the mouth because the ceramic needs to be melted at a very high temperature which cannot be done in the oral cavity. If your crowns have a warranty certificate with them, they can be replaced for such damages. The best step would be to get yourself evaluated for the current condition of those Crowns. And the option of replacing the Old Bridge with the new one is always there if the repair work is not possible. Regards