I have 18 Salmon Faverolle chicks that are 4 and a half weeks old. I hatched them and know they have been completely healthy up till today. Kept them in the basement for first three weeks. Moved to barn a week and a half ago and put in brooder. Brooder was clean, sanitized and new shavings used. Today when I got home, 1 was dead, I had to dispatch one and one is alive, but has blood on its bottom. All others seem fine - all are eating and drinking well. I cleaned the water and put in probiotics. Any idea what it could be? What should I do? WORRIED.....