We bought a model 1270 GQF hatcher secondhand. I'm wondering if we have the vents set ideally. We are getting a decent hatch rate but not quite 80%. Last hatch we had three fully zip but not hatch and die. This time it was 3 on the bottom. It happened to some last time and at least one was on the top, but I can't remember how many and location. We messed with the vents to get the humidity up because our 1st hatch in it, we couldn't get humidity above 20%. There is no humidity system in it; I think it was there before but nothing now. I set a pan of water on the top shelf and we put a humidifier right behind it. Then we started closing vents and were able to get humidity to 50%. The chicks zip all the way around and their fluff that is exposed becomes dry and fluffy but they never make it out. I've helped a couple out successfully and some unsuccessfully and some have already been gone. One looked like it drowned in it's own yolk; its little mouth was open and there was dried, yellow, crystallized substance on its face and in its beak. It just seems odd that they are dying fully zip, and I'm wondering if it's something were doing wrong. The hatcher stays right around 98-99⁰. They spend the 1st 19days in the matching incubator with auto turners. I'm attaching pictures of the vents. Thanks for any help.