You are using horizontal water nipples from day 1 and they are actually using them and getting water? Is that your only water source? I tried my chicks on the horizontal nipples at 2 weeks and they don’t seem strong enough yet to use them. The horizontal nipples I got from a friend so not sure what brand they are or if that matters. I also ordered some RentACoop brand horizontal nipples but haven’t tried them yet to see if there is a difference. I now keep the bucket with horizontal nipples in the brooder with a quart jar waterer to be sure they are getting enough water. When I manually push and water comes out, the chicks

come running to drink

but I haven’t seen them do it on their own.