it actually depends on your medium. are you Hydro? your range is 5.5-6 (not positive, i dont do hydro). if its soil, the range you are looking for is around 6.3-6.8 (on average 6.5)
yeah the medium depicts PH but ask Uncle Ben and he will say pfffffffft ph why bother, he doesn't care about ph and produces incredible pot. anyways what "they" say is good is;
Soil: 6.5-7 during veg and 6-6.5 during flower
Soilless or Hydro: 6.5 for veg and 6.0 for flowering
hope this helps, but read Uncle Bens thread and he pushes the whole " who cares about ph, read your plants and feed them accordingly, he say ph is not a problem it's always other things like nutrients, temps, humidity and watering schedule " I still ph properly though ~ BCbuddy