no difference between fermentation temp issues between extract and AG. the impact depends on the yeast strain. if it's the weihenstephaner strain, it will ferment down into the low 60s. into the 50s it probably flocculated out, but then started back up if you warmed it up again.
temp control is pretty important. a temp controller and some kind of brew belt or heating blanket around your fermenter to precisely control the temp would help you a lot.