I have some yeast cake and wort that was saved from an apa. I boiled the wort, cooled it down and pitched the yeast. place it on a stir plate ( Home Made ) for 2 days now, my question is what is a sign that the yeast is healthy, I haven't noticed anything different from day 1, no co2 or krausen. maybe because of the spin action?. Brew day is tomorro and getting a little concerned.