if your gonna water every other day make sure your pots have good drainage...and make sure ur room has good air circulation add a fan if you dont have one
i dont recommend miracle grow try to stay as organic as possible its not to late to change
and yes your pot size might be your downfall, you dont want your roots to be crammed in the bottom of the pot make sure theirs alittle room for them..so if u have an 8" pot try going alittle bigger and see if it helps
also 50 degrees is alittle cold but not too bad..try to stay above 60 if possible