Rep agent scanner for each replicated database

Dears, kindly help in this issue:

We have WS pair primary db1 and standby db2 it is managed by repserver1

And MSA managed by rep server2 and its source is WS logical connection and its supscription is db3

If db2 is sync with db1, but db3 is out of sync and want to reynce it with db1 , for performance issue and to not affect db2 , is it better to use multiple scanner for primary db1 rep agent, if yes, is there any docs for similar issue

Regards