We also didn't have a major hailstorm in my area--late hailstorms destroying everything has been one of my biggest growing issues lately.
I also think the chicken poo may be part of it. The chickens made a big mountain of poo in one corner of their run, and it's aged into a massive pile over the year. It just looks like dirt now, but I scraped it all out (2 wheel barrows full!!) and mixed a bit into all the gardens. The one garden I didn't put any in because I finally ran out is the only one which isn't growing as well.
If that's truly the secret though, the chickens never have to lay another egg, the poo will be enough payment for the feed!