Don nailed it pretty much. I have a buddy I set up w/ an Ecet. A year later, his string was down on the riser it had stretched/crept that much, I just happened to catch it as he was going hunting.

Since you are no doubt replaying the shot in your mind, I'd offer the suggestion did you spin test those bheads?

What bheight are you using? Some of the Excal crowd claim there's a 'sweet spot' at 1 1/8" which is w/ serving just touching the inside of high mark, I tend to agree. The bows seem to really like it and it gives one a little more leeway w/ a stretched string.

The main problem w/ too low a brace height is the string slapping the riser and trashing the serving and/or string.

New strings are infamous for stretching, although they have been getting better. Until I started using 'Boo's', I used to set the bheight on FFF's about 3/8" above high mark and leave the bow c0cked overnight a time or two. Eliminates a few adjustments.

Sorry about the deer, that's rough!