Recording via microphone has no treble

Experienced with audition, but haven't used it to record for a long time.

I just got an AKG P420, which is plugged into a Mackie 2x2 audio interface.

I'm using the ASIO drivers and I've tried enabling forced settings. I've made sure all the levels are 100% in the settings panel for the interface, as well as windows device settings.

When I record audio the track has no treble. This is visible in the waveform - bass and low-mid frequencies seem unaffected.

Aside from the USB cable connected to the PC, the audio interface has both a headphone jack output and a line output. I've monitored both of these whilst recording and the signal comes through perfectly clear from both outputs - so either the PC/Audition is interfering, or there is something broken in the audio interface itself, after the signal is processed but before it is sent back through the USB cable.

I haven't been able to find any similar issue in the forums, to know if there is any Audition setting which commonly affects this.

TIA!