Water Pressure Issues

Hi all!

I am having some issues with the water pressure since yesterday. When I open any faucet, it initially starts out with the same pressure as usual, but quickly loses about 40-50%. I checked the whole house for leaks but didn't find anything. It affects both cold and warm water.

The house itself is pretty new and has a well + gas heater setup, as seen in the picture.

Any ideas what could cause this? I will probably call a plumber but thought it is fine to wait until after the long weekend.

Thanks in advance!