Hydro Hen looks like more of a broad spectrum probiotic. I think it would be a great idea given the ravaged GI tract.
For really sick birds, I do the oral dosage to make sure they get what they need.
I absolutely understand why you would be hesitant about the ground. I have a $35 solution. A product called Oxine AH. It's chlorine dioxide. Go read the website. It has multiple used for chicken health. You'll be wondering why it isn't marketed more aggressively to chicken owners.
I mix up a few gallons and spray the coop and my yard in spring and fall or if I get an outbreak. I often have ducks, geese, doves, cranes and cowbirds land in my yard. My girls free range, so they will get exposed to different strains.
Oxine AH takes care of that.