To know if it's getting worse, generally the bird will show a decline. Lethargy, drinking a lot of water, not eating, etc.
Right. Those "extras" may not smell like that in the bag, but once consumed and if not being processed and fermenting (sitting in the crop/gut) they can take on a whole other odor.
It's just a suggestion to see if eliminating the extras makes a difference in the odor you detect.
Post photos of the chicks, brooder and poop.
I have no idea about the mama chick feed, but it looks to be whole type feed (not pellets or crumbles) so it's important to provide grit so the chicks can process that feed.
Check her crop first thing in the morning before she's had anything to eat/drink after a night's sleep and see if the crop is empty. This will give you more information.