Help - Sick 3-week old chick

[Omelette]

One of my 2 baby chicks appears to be sick. She's collapsing a lot onto her knees and walking like she's drunk. Stepping on her own feet. Also shaking. She closes her eyes a lot. When she poops, she almost collapses and has to use her wings for balance. Any idea what might be going on?

Thanks!

 

[catterbug]

Could it be Marek's? I am new to this whole chicken thing but maybe that is what the problem is. Did you get your chicks vaccinated?

 

[Omelette]

The chicks were not vaccinated.

It looks like it might be marek's. I read some threads here, and it seems to effect older birds, not 3 weeks old.

Does anyone have experience at this age?

Her head is very shakey and she's tending to fly from point to point because she can't walk well.

Thanks!