I listen to WHYY almost every day, and noticed something was wrong about two weeks ago.
I travel between my home in Norristown and Lancaster a couple of times a week using 202 & 30, and usually have no problems receiving them until I get west of Coatesville, when WETA starts cutting in. On one of my trips (Sept 14, I think), WETA started walking all over them not far past the PA29 exit heading south on 202, and by the time I reached Thorndale WHYY became unlistenable. At that time I thought it was tropo--not only was WETA there, I picked up WFUV 90.7 with enough strength to get RDS data. But when WHYY's reception was no better a few days later, I checked their webpage and saw the notice about the antenna problems. They must have upped their power a bit last week, as the WETA problems in the Exton-Downingtown area went away sometime around Sept 22, but their signal west of Thorndale at that time was still noticably weaker than normal.
As radioskeptic noted, WETA is grandfathered with facilities above Class B limits, and that certainly isn't helping matters for WHYY west, south and southeast of Philly.