Without an age on those does the presence or absence of milk don’t mean much. They could be 1.5 year olds and wouldn’t have milk anyway.

Even if they’re in the process of weaning or have weaned the mammary glands will still have a milky substance in them. Always cut into the sack and check rather than pulling on the nipple.

Two things. I suspect some of both. Could be a coyote predation issue combined with low reproductive success from skewed sex ratios.

Old barren does are like unicorns. It’s a myth. Does produce fawns until they die.