I recently had the same issue, losing 12 of mine. We eventually killed the one fox (legal here) and have been setting a live trap for the other. However, I bought a solar powered radio that I play the weather channel on all day, since fox are scared of people), a motion detection alarm that emits lights and a high-pitched alarm, and 100% wolf urine to spray along the perimeter. The fox hasn't been since - two weeks now. I don't know if these things actually worked or if it decided to move on but it was here the day before I set it all up and now it's not, so... Anyway, good luck and I'm sorry for your loss.