I don't think you are doing anything wrong, so hang in there. The first year of chicken keeping can be hard. In my first year of chicken keeping I lost 8 of 16 birds -- some to predators, but others to impacted crop, or unknown causes. To put that in perspective, in the last two years of chicken keeping I have lost 1 bird out of 20. What changed?
First, there is going to be some natural selection going on. Every soil and piece of land is different in terms of the kinds of microbe and parasites that are in there. Putting a new chicken on a new piece of land is a big unknown. Some chickens will adapt well, other might not. As you keep chickens over the years, they will get hardier, and their offspring will be hardier (if you are breeding them).
Along those lines, I have found the best way to ensure hardiness, is to get chicks exposed to the local soil and conditions as soon as possible. Ideally this happens if you have a broody hen, who can raise the chicks in the coop from day 1. But, even brooding your chick with a pan of dirt from your yard can make a big difference. The younger they are exposed to "bad" things, the hardier they will tend to be. I know this doesn't help your situation now, but it might down the road, especially if you end up replacing some of your flock.
Second, you will learn what works for your chickens -- which may be different from what is working for someone else's chickens. It will take time to learn what that is, but you will learn it. For example, I used to stress about spotless water dishes, coops, etc. At the end of the day, I found that I was happier, and my chickens healthier by keeping things clean, as opposed to spotless. I also allow them to range in a large chicken yard, and supplement their diet in ways that violate the "10%" treats rule, but works well for my my chickens. Pay attention, be patient, try new things.
It is a learning curve. You are at the steep end of it now. Don't beat yourself up about it. It will get better.
First, there is going to be some natural selection going on. Every soil and piece of land is different in terms of the kinds of microbe and parasites that are in there. Putting a new chicken on a new piece of land is a big unknown. Some chickens will adapt well, other might not. As you keep chickens over the years, they will get hardier, and their offspring will be hardier (if you are breeding them).
Along those lines, I have found the best way to ensure hardiness, is to get chicks exposed to the local soil and conditions as soon as possible. Ideally this happens if you have a broody hen, who can raise the chicks in the coop from day 1. But, even brooding your chick with a pan of dirt from your yard can make a big difference. The younger they are exposed to "bad" things, the hardier they will tend to be. I know this doesn't help your situation now, but it might down the road, especially if you end up replacing some of your flock.
Second, you will learn what works for your chickens -- which may be different from what is working for someone else's chickens. It will take time to learn what that is, but you will learn it. For example, I used to stress about spotless water dishes, coops, etc. At the end of the day, I found that I was happier, and my chickens healthier by keeping things clean, as opposed to spotless. I also allow them to range in a large chicken yard, and supplement their diet in ways that violate the "10%" treats rule, but works well for my my chickens. Pay attention, be patient, try new things.
It is a learning curve. You are at the steep end of it now. Don't beat yourself up about it. It will get better.