Ok, did you calibrate the temperature? You should never trust the temperature that the incubator gives you right out of the store. Best to double check it with a calibrated thermometer.
I would also make sure you put a humidity meter in there so you can check on that.
If you can’t do that i would weigh the eggs and see if they loose the right amount if weight on the according days. That way you know if they lost to much weight you should put more water in, if they lost too little you should put less in. If i say more orcless water, i mean the surface, not the amount. So don’t fill the same bowl with more water but put in a second bowl, or put a smaller one if you need less. The ideal weight loss would be
Day 5: 3%
Day 7: 4%
Day 10: 6%
Day 14: 8%
Day 18: 11%
I put that into an excel file where i put the beginning weight of each egg and it gives me the right weight on the according days. I can also put the weight during candling at the according days and it will tell me what average all of the eggs lost so i can adjust the humidity accordingly.
I have no idea if i can upload excel files here, otherwise i’d be happy to share it.
After day 18 you stop turning and candling and put them out of the turner if you have one. Then you upp the humidity to make sure it is nice and moist in there for them to hatch. Always make sure your incubator vents are open at this point so they don’t suffocate.
No more candling at this point! The chicks need to be able to position themselves for hatching.
I wouldn’t think that too much candling has anything to do with it unless you take them out and candle them several times a day or if you treat them roughly which i wouldn’t suppose you do. The henn leaves her nest once a day for 30-60 minutes too so that shouldn’t affect your hatch rate.
Any more questions? I’m happy to help if i know the answer. Good luck!
