So sorry you lost so many. My eggs arrive next week - I also have a Brinsea. But now I'm worried. I only ordered 6 eggs. Hopefully some will survive.
The remaining chicks appear to be healthy. Other chicks in the brooder are RIR, Red Leghorns, Malines and Silkies. All are doing well but these didn't seem very vigorous.
My chicks get a cocktail in their water.
I have a 1 gallon waterer in the GQF brooder and it gets 1 TSP Poultry Cell, 1 Packet Chick Saver Electrolyte and 1 packet Chick Saver Probiotic.
Has worked wonders so far. White Faced Black Spanish, Lloyd Minor Blues and Cuckoo Bluebars are the least vigorous and most prone to death chicks I've had.