This started after a handyman snaked a bathroom sink pipe to clear blockage. While it's possible that he did not cause the problem, it's the only thing I know of that changed just prior to its start.
I had all plumbing in my downstairs condo replaced with copper in the mid-1990s. (The building has two units downstairs and two upstairs.) A plumber who took a look thinks this will be solved by replacing a galvanized pipe that goes from the front of the building to my unit at the rear with copper. Even if it raised the overall water pressure a bit, would that necessarily affect the faucets while the toilet is flushing?
One piece of advice I found to someone else on a forum was if the kitchen faucet is affected too, "it is most likely an issue with the main or pressure reducing valve." Someone else suggested, "A blockage may be something as simple as a valve that someone partially closed--perhaps to make a repair--and forgot to reopen."
When the plumber who came by did something in the crawl space, my tenant said the overall pressure got better, but the trickling stayed the same.
Any agreement or disagreement with these potential cures? Or new suggestions?