Re-scanning may not make a weak station stronger. If a station has changed their actual frequency due to the repack, then yes, your antenna will likely find the new frequency, but it will not cure a weak signal.
What you are most likely encountering is a ‘temporary’ reduction in power from those now ‘weak’ stations. In my market, for example, a few different stations use the same tower.
The repack has created a situation where some stations have to install new equipment.
At the tower in Needham, the station that has their equipment near the top of the tower has to do some work up there, so a few of the stations with equipment lower on the tower must reduce their power to protect the workers while they are on the tower.
Some of this work can takes weeks or months, by the way. This is most likely what you are seeing.