So this has never happened to me before, but I had my 1st explosive fermentation. I'm pretty sure this is because I have been slowly pushing the maximum of what I can squeeze into my conicals. I brewed the same size batch two weeks ago using Nottingham and didn't have an issue, that was fermented at 19'c. This week was with American Ale (Wyeast Labs #1056) [125.00 ml] at 20'c. Both were around the same SG. Just shows what 1'c and Liquid yeast can do.