My profession is industrial pumps. Let me give you the basics.
First, pressure is resistance to flow. 1 of the 2 things listed has to apply.

If you are seeing the normal amount of water volume coming back into your pool, then there is nothing wrong with your pump. A lower pressure reading indicates that something changed between your pump and the pool. That something would be in your filter. For some reason you have less restriction.

If your water volume back to your pool is less, and less pressure, then you have a different problem and I don't have enough information from you to troubleshoot it. This type of pump would only lose volume suddenly if:
The intake line is restricted (then it will sound like it's pumping gravel).
If the pump impeller got some debris in it, which you would have to clean out.
It's not turning as fast due to an electrical problem. (this one is not my 1st choice).