I haven't ever raised chicks under a broody hen but when I used to raise White Chinese geese, the mother goose would push any bad eggs out of her nest. They know.
Gee, Barred Babies, this is how I ended up w/2 Hovnabators--very similar situation to where you're at right now.
I second what LaMike said, put your lockdown eggs in the bator you know is stable & working well & move the last egg -- I myself couldn't pitch it, because it rocked in the water, it's alive in there. I once opened an egg I *thought* was dead a few days prior to the rest pipping -- it wasn't, but I killed it when I opened the shell up. I will never forget that. I will always give mine every chance that I can - within reason, yes -- but, I can't bear to kill something when it hasn't even had a chance to live yet...if it doesn't make it, doesn't hatch, you can always use the LG for a brooder, and at least you tried. (Yes I am way too emotionally invested in my animals. Guilty!)
This is one of those situations only you can decide what's best for you to do as far as the remaining egg. It may be hatching late because something is wrong inside & it won't make it even if it does hatch. Or it may have just been one of the "younger" eggs. I know, my logic process runs in circles, I'm sorry. I would be in a lather right now I were in your shoes, trying to decide what to do.
