So i ve been playing nl25sh zoom p* more and more this month (before it was not a case), and i see this month that my 4bet/line was working fine up to some point, then it seems like regs got better sample on me and adjusted

graph:
http://i.imgur.com/G1mrVAz.png

questions are:
what should i take into account to select proper 4bet/fold lines when not having a premium holding ?
how should i check myself? how can i learn how i am perceived by others

any ideas would be greatly appreciated !
cheers