why my battery life is low?

when i purchased this macbook (macbook pro 2012 mid, 13", core i5), it worked good and the batery life also was good. it was around 4-5 hous. but recently the battery life is going down and tried some ways. (calibrating graphics, removing uneccery programs.) now this macbook works up to around 2-3 hours. battery cycle count also 70. it's been around 7 months from the purchased date. recenly i've been playing League of Legends on my macbook. is it affecting to my laptop? i mean "gaming"?

and it heats up. but it didn't happen before i play League of Legends.

all updates are up to date.

what do i do? please help me.