One chick hatched from 5, advice on how to proceed?

[FloorCandy]

OK I'll leave them for now.

As an aside, should the brooder height be set so they can stand under it or so there's just enough room to squeeze under it when sat down?

The brooder plate should be set so the height of the chicks back touches the heated plate when they stand. I make the legs on one side of mine slightly higher so they can choose the best height for themselves.
As far as your other eggs, try having the brooder close enough so the eggs can hear their friends chirping, it encourages them. You can also play chick sounds for them off of a recording. I do my best to always leave one in the incubator to call for the others and I find this really helps the slow eggs hatch.

 

[Chicalina]

congrats on your babies. Have you shown them how to eat and drink? Newborns can be a bit thick that way, and it might explain the random pecking

 

[Jay Cartay]

Both eating and drinking fine now

I've just now popped the two eggs that were left. One is a chick but no movement or noise whatsoever so presume it didn't make it? Other is harder to tell so don't think that made it either. Still daren't give up and throw them away but I guess I need to.

 

[Chicalina]

if you have broken into the shells already and there is no movement, then i wouldn't toss the eggs without checking 100% they arent alive

 

[Jay Cartay]

OK so just now I've properly opened one egg up after zero movement. This would have been day 25. Its a fully formed chick. Not breathing. No movement

It's hard to take. I can't see any reason why it didn't make it.

I did take a photo but not sure I should post it.

 

[Chicalina]

that is really sad. I've had quite a few like that recently. They must have died just before hatching time and I don't understand why either. They didn't even pip internally. Mine were under a broody so I'm assuming it must have been heat/humidity/genetic issues which were all outside my control.

It was weird because most of the DIS of the first batch were white (black chicks did hatch) and on the second batch the DIS were black (white chicks hatched).

 

[RoosterML]

OK so just now I've properly opened one egg up after zero movement. This would have been day 25. Its a fully formed chick. Not breathing. No movement

It's hard to take. I can't see any reason why it didn't make it.

I did take a photo but not sure I should post it.

Was your humidity to high during the whole incubation? 30%-35%days 0-18........ 35-45 days 18-21