Early weak fawns

[Romeacres]

I have been mulling this over since it happened to a good friend of ours.
His deer had been vaccinated at the same time as ours. He gets his feed from another deer ranch but all of his does fawned a month too early and all 22 fawns were less than 2 lbs and too weak to survive. Couldn't even get up.
What in the world would cause every single doe to drop way too early?

[Wooden acres]

It's really hard to say with your vaccinations and all but if I had a bunch of cattle calve early like that I'd be checking for lepto asap !! Just a thought it could be a bunch of things !!