Ok, I went out and emptied all the skimmer baskets and pump strainer. Not sure how to check the impeller. Ended up with same pressure. Then I backwashed as usual and it went back to same pressure. You are right that an obstruction could decrease pressure since turning off the main drain or skimmer will do the same but they are all on. I have a return jet in the shallow end that blows close to the top of the water so I can visually see the circulation and it is better than it has been in the past. All the skimmers seem to have good circulation. When turning off the main drain pressure drops further as it should.
I've always had a problem with the pressure running too high in my opinion at about 26 psi after a backwash. I would wait for it to get up to no more than 35 psi before backwashing again and it would always go down to about 26-27 psi. Now it is running at 20 psi which is more in the range of where it should be.
If the flow, from the return jet, in the shallow end is, visually, at least or greater than it usually is and all the skimmers seem to be sucking normally, am I right to assume there is probably no obstruction?
Thanks for your help!