Ok so i'm brewing my first lagger. i pitched my 2007 wyeast at 70 degrees as indicated by the package and i kept it at this temp for 4 days. in this time fermentation started and i got a great bit of head. now theres no head and the air lock is barley bubbling. i just looked up the temp for this yeast on their website and relized it should be 48-56 so i just adjusted the temp. at this point if i killed the yeast can i add more? or just tough it out?