Hi NKOUAMBIA,
Thanks for your update.
Based on your shared screen shots with details, we suspect that you have different fonts in label text. We would like to say this our component bootstrap theme does not change the browser text font style. We suggest you check once again your application with label text font style changes.
If still you have facing the issue, then please share your razor page with _host.cshtml page of your dropdownlist component application. That will help us to provide exact solution as earlier as possible.
Regards,
Sureshkumar P