Did they get a treat last night?I have a really sensitive nose, but honestly there's been zero smell until this morning. Hence my shock. First week, with no changes: no smell. So I did a slightly deeper litter on Sunday when I moved them to the new bigger brooder and thought I was set for the week. Last night: no smell. This morning: HOLY CR*P! Quite literally.
You can try giving them some chick grit, yogurt and a bit of food grade DE.