Eero 3-Pack

A few days back we installed an Eero 3-Pack to replace our Verizon Fios G1100 wireless router as follows:  1st Eero - connected to the Verizon modem in the ground-level den, 2nd Eero - located in the dining room on the first floor, and 3rd Eero - located in a bedroom on the second floor.  The Ereo located in the bedroom keeps going red and dropping the signal.  Should the Eeros be placed directly above each other floor by floor for the best signal since the signal goes vertical?  Our townhouse is 1,700 square feet and I assumed that each Eeros would cover one floor but that doesn't seem to be the case.  Initially we had place the 3rd Eero at the top of the stairs between the bedrooms so that it was more centrally located but the light always remained red.  Any advice on placing our Eeros would be appreciated.  Thanks and regards, Bob