Free-Range Chicken More Disease-Prone?

[MotherHen007]

I free range my chickens: 10 hens, 1 rooster, 5 15ish week old pullets and 2 15ish week old roos. They have access to 5 wooded acres all day since we moved here 5 months ago. Before moving here they had a large run (and I only had 1 rooster and 6 hens). I am so happy with them foraging and the cost of feed decreased drastically and not to mention they have all but eliminated ticks from the property, however I am perplexed. Prior to moving and letting them free range, we never had any illness. I’m the last 5 months I’ve had 2 die to predators (not surprising we handled it by fencing property perimeter and getting a couple cats and big dog), 1 die from illness (of course she was my favorite) and the rest of them have sneeze/cough, snot, and gagging. I am super upset. I bought antibiotic soluable in water but it’s hard to do since I don’t confine the chickens and therefore they drink from multiple water sources on property. I bought diomatious earth hoping to help if they have any parasites. I’m just at a loss. If anyone here knows how to help I appreciate tips. My husband thinks we should built another run and keep them confined because they seemed healthier that way. I’m starting to agree…