All of a sudden, muffled sound

So, I've been using the Focusrite Solo 3rd gen for just over two years, mainly for practicing at night. I use it with my HD600 headphones with a stock adapter.

​

Recently, I discovered that any VST I was using started to sound sort of muffled: I have to either drive the amp-sims really hard or to use built-in equalizers to raise the upper frequencies to not get a sound like I'm listening through a couple of blankets. The recorded tracks that I made in GarageBand sound normal though.

​

I thought that the problem may lie either with the USB cable or with the macOS Ventura, but then I realized that I am getting the same muffled sound through the Direct Monitor.

​

Which brings two questions:

1. Is my interface dying?
2. Will using an external headphone amp through the line-out port alleviate the problem until I save enough money to buy a more decent interface?