I’d say pretty high.
Eggs don’t really need to be turned after about 14 days. Turning is really important early. That’s when the body parts are forming and turning helps them form in the right place. Turning also helps keep the yolk and embryo from sticking to the side of the shell, but the chick develops a membrane to protect it from that happening. Otherwise it would run into problems when it got too big to not touch the inside of the shell. So don’t worry about the turning at all.
Losing power like that is not good, but it’s probably not fatal, especially if they only dropped to an air temperature of 85. Air temperature is not that important. What is important is the temperature of the chick inside that shell. Due to thermal mass, it takes a pretty long time for that to really cool off. Plus, at that age, the chicks are producing some body heat of their own. There are all kinds of stories on here where something like that happened and people still got great hatches.
Last year a broody hen went back to the wrong nest. It was obviously hours before I noticed and put her back on her eggs. Those eggs were ice cold to the touch. She hatched 11 out of 11. What really surprised me was they were more than a full day early.
