I am as of yet unsure, mink apparently get in a gap 3 fingers wide. No chickens left, but I have had 5 delivered this morning. All fluffy and chirpy.
I am moving the pen, the area was a dozen times as large as needed and was double fenced (with electrics) but it's maintenance was too much so I'm building something closer to the house. I'll certainly post some pics!
I'm sorry to hear to hear about the fledgeling and now the loss of the hens. Minks can get through incredibly small places, horrible little things. There is a bunch of articles on BYC on the different predators and how to protect your flock and predator proof your coop: