Update 5:
Sad update. The speckled sussex chick was dead in the run being picked apart by the other 3 hens when I got home from work. Not sure what happened. I noticed mama had moved the nest and they were not in same location as this morning. There was no blood or carnage in the coop, so I'm not sure if maybe the chick had died and hens got ahold of it?
I also noticed mama does not really show the babies food or anything. Like, my husband put a little bit of all flock by her and she just started eating it and didn't call chicks to it. She clucks to them frequently, though, and they peep at her.
The 3 remaining chicks are doing well.