Very true, i would just doubt that many dogs, after performing well for say 4 seasons, would suddenly 'become' shit one night, on rabbits?
After 4 seasons and on rabbits if the dog had been doing well, you would deffo look for other causes to a dog underperforming, thats a no brainer imho, but if there are no other causes then it may just have chucked in the towel.....it happens.
who mentioned "one night" you know a dog well enough after that amount of time to notice a change,put it down to a off night?give it a break?only to go out again and watch it all happen again,like wilf says