Chicks that are slowly dying,

[Frizzll Farm]

Hello I got my batch second batch of meat chickens last Friday at a day old. I do order the White rocks, and in Canada they are the fast growing meat birds. I just am wanting to see what others think. My first batch are 6 weeks old. ALL 153 are still alive and well and steadily growing. my second batch of 150, on the other hand are NOT doing well at all. They have two heat lamps and are bedded with shavings. I have had 20 chicks in the last week die. 15 over the first two days. When they arrived I dipped everyones beak in water and showed them where the feed was, checked bums and went along with my day checking periodically. Day two bum check after loosing 5 (bums were fine) I noticed that quite a few of the chicks had empty crops, had eyes closed and just very weak in general. I say they are lethargic. Drinking only when taken to water and then two steps and they lay back down. Wont eat any food. I want to know what the possible reasons for this are. Why my first batch has been doing great and this one just looks sick and un healthy. Vitamin supplement has been given in their water also. other than that I haven't done anything different. I want to confront the hatchery I ordered from but want to make sure nothing has been done on my part to make these chicks not thrive. ( I also hatch my own chicks and raise them so I'm not new at it)
Thanks so much in advance.

 

[lightchick]

How old are they? I'd start giving them Corid. Do they have blood in their poop?

 

[Frizzll Farm]

They are a week old, I do not see any blood in their poop. looking to possible not treat with anything as in ten weeks if all goes well with the remaining they will be dinner.