Hi @Fernando_Garcia! Welcome to the community. 
I haven't been able to fully test this just yet, but I think I might know what's going on here. Which credentials are you using in order to connect to your RDS cluster via the command line? I ask because the credentials included in the YAML configuration files are not the same credentials that the Retool instance uses!
When connected via PSQL, you can see the additional roles (\du) and databases (\l) that Retool has created:
This is also noticeable when looking at the connection details in Retool:
All this to say - it should hopefully be enough to create the vector extension in each of those other databases in order to get everything working as expected! Let me know if you run into any additional issues.