Yes, you can reimport one single chain at a time. Usually, this is what you should do, as it is better not to reimport wallet unless necessary.
To reimport a single chain, navigate to the accounts page, select the wallet you need to reimport, and click "show all accounts" here:
That will bring up a list of each chain the wallet has transactions on. Select the chain you need to reimport, and click reimport:
This will only reimport the single chain.