Yeah. If you are really worried about safety, clean the coop out really well, clean the water every day or two, and get them in a run. The first two are mandatory when caring for chickens, but the last one is just a suggestion.
To keep them safe from predators, maybe get a dog / chicken kennel to keep them safe while also giving them plenty room (depending on your flock. Larger one for a larger flock!) For the sickness, are you cleaning out the water daily? It might be a cause of the sicknesses.