How can I implement syntax highlighting across the entire project files in VS Code?

In my case, while developing a Blazor web app, I found that some files have syntax highlighting and others do not. It primarily consists of HTML, C#, and JavaScript, which can occasionally be combined into a single file.

Here's the screenshot of it:

It appears off, especially if the JavaScript code expands in size.

And here's the VS Code relevant information (VS Code > Help > About):

Also, note that I am on Windows. Yet, I have no idea why it occurred.