wobbly chicks loosing the ability to stand

[New to Chicken Life]

I am at my wit's end. This is my first-time raising chickens. My chicks are 3 1/2 weeks old, and they are all starting to lose the ability to walk correctly. Wobbly at first and then losing the ability to hold self-up. They are not all doing same time, meaning symptoms are occurring at different times. I introduced Poultry Cell 3 days ago and electrolytes to their water. Am I not feeding them correctly? They are getting toasted seed bread, hard boiled eggs, and greens diced together. Poop is also a black color. One chick died today. I noticed them eating pine shavings from the bedding. I just removed the pine bedding hoping that was the problem. Should I change their diet? If so, what should I feed them. Can I reverse this problem? Please help. I am at a loss. What should I do?

 

[Eggcessive]

They need to eat a balanced chick starter grower which you can get at a feed store or TSC. I would get some right away.

 

[Lor]

Do they have chick grit to process the food you are feeding?