Boost wifi poor connection

Hi there, I have the Arcadyan Hub and 2 boost wifi.  The Hub is placed at the south end of the second floor of the house, boost wifi 1 is placed in the middle of the second floor, and boost wifi 2 is placed in the garage on the ground floor at the north side.  Boost wifi 1 is hardwired to the Hub, Boost wifi 2 is wireless.  The distance between boost 1 and boost 2 is about 15 ft.  But somehow boost wifi 2 always have poor (amber) signals and I suspect it connected to the Hub instead of connecting to the closer boost wifi 1.

Is there a way to set the boost wifi 2 to always connect to boost wifi 1? I have a small house which is about 2000 sq ft in total ground floor plus second floor.

Thank you.