So after 2 weeks in the fermenter I decided to take a FG reading and it's come in at 1.020 when it's supposed to be at 1.012, at the start of fermentation for roughly 4-5 days it was bubbling away had a lot of krausen at the top but now that has dropped down to the bottom. I have raised the temp to 20 celcius, it has been at 18 the whole two weeks. Not to much activity since raising it I don't think, would adding another smack pack of London III do the trick?