I never go to feed stores without first walking down the aisle and checking the mill date of all the feed. Then I decide which bags under 2 months old that contain the protein and calcium percentages I need. Then I may differentiate based on ingredients but the first two tell the tale.
The dark specks may have been alfalfa. None of it looked like mold to me and there is no way I would trust the opinion of a feed store employee.
The feed store by my house only carries one brand of layer and one brand of start&grow. The former is normally fresh because there are lots of people around here with small flocks of layers. However, locals only have chicks in spring so their starter can be as old as a year. I quit asking what the mill date is when they told me, "you don't want to buy it".
To get fresh feed, I have to cross the bridge into the next state. The
TSC there is good about rotating product to maintain freshness but they are a little higher in price. The Farm & Home is much less expensive and has the best selection, but if I don't check the mill date, I could be buying old feed.
Everybody's nose is different so I wouldn't put a lot of faith in that. A reputable brand that is fresh and the correct protein and calcium levels (determined from the guaranteed analysis tag) is all that concerns me.