I have a small self turning incubator. When I turn my eggs twice a day, the temperature drops to 30 degrees Celsius and takes about 10 to 15 mins to warm back unto 378. Is this ok? Will the temperature drop effect the eggs?
No it wont effect it. The air temperature reading has little to do with the internal temperature of the egg. Air temp inside incubator fluctuates constantly and drastically when opening the lid. The mass of an egg stays constant, the embryo is at the center of this thermal mass.
x2. The other thing to keep in mind is the mamma hen. When a momma is broody and incubating eggs, most of the time she stays on top of them. But she does not stay there for 21 days without moving. She does get up to eat, drink, and poop. I have seen my broodies up and off of the nest for sometimes 30 minutes or more. I use to worry because the eggs would actually feel cool to the touch and I thought for sure she was a bad mom and let her babies die. But most of the eggs always hatch. So if you look at your eggs that way, you are only letting your incubator cool down for a short time. It will do no more to effect them than the momma getting off of her nest.
Also I have read some studies that show that hatch success goes up if the eggs are allowed some time every day to "cool". I am not talking about letting them get cold by any means, but these studies were showing that eggs that were allowed to "cool" (or basically the bators were not in heat mode) for a short time every day actually had more eggs hatch. I don't remember all of the numbers off the top of my head, but for some reason 20 minutes of non heating in a 24 hour period sticks in my head. And again off the top of my head I think it was like a 1% increase in hatch rate. Not a lot but did show an increase.
Don't worry, sounds like you are doing things right!!!