Sick? Silkie Chick

I did post it on the Raising Chicks section but didn't get any response, so I was thinking I had posted it in the wrong area.  Maybe someone here could help me?

I have two groups of chicks, one set of four that are 2.5 weeks and are large fowl and another set of silkies that are 1.5 weeks and they all live together.  One of our silkies is very tiny but has doubled her weight in the 8 days we have had her to a whopping 1 oz.  My concern is that she sleeps more than the others.  She will be sleeping while the others are scratching around the brooder and she has done that a lot today.  She seems to have normal poo though occasionally, twice, having pasty butt that I have cleaned.  There is vit. and electrolytes in the water.

So my question is is this normal for the itty bitty wee ones or should I be concerned with what I consider to be excessive sleeping?  How do I know if she's not okay?

I guess I would find poly vi sol vitamins at the feed store?  

She has eaten and does drink and the times that I have taken her out of the coop to run around the bathroom with the others she does.  She pecks and scratches with the best of them but it just seemed like today she is sleeping so much and doesn't have energy.  She's not peeping or anything.  I guess some vitamins and just leaving her be?  The other silkie which is larger is acting more "normal".  She's just so, so small.  I worry about her.

Thanks for responding!

What is a crop???  How do I know if it's full?  I am a newbie. 

No it's not full.  I'm actually surprised she made it through the night.  I really didn't think she would.  When we took all the other kids out this morning to run around the bathroom which they love she continued to lay there face down in the wood chips.  When I put her face to my ear I can hear her breathing in and out as if she has a little stuffy nose, but I don't see anything.  She's still continuing to just lay there.  When I pick her up she just keeps her eyes closed.  I filled my nail with water and put her beak in to drink and she did a couple of times.  I checked the brooder temp.  It is exactly 90.3 degrees.  I found out where to get the poly-vi-sol vitamins and I am going to go get those.

Let me tell you how small she is.  I can place her in my hand and wrap my entire hand around her so that my fingers touch my palm like you are making a fist with her little head poking out where my thumb and forefinger touch.  I am a 5'4" woman so this is not a large man hand and this is double her weight from when we got her.

I really want to see her make it.  I didn't sleep at all worrying about her.

The crop is squishy.  I was just massaging it trying to find a blockage but it's just squishy. Normal?

I also haven't seen her poo in quite awhile.

So after all of your suggestions and spending all of this morning on the net I think it's sour crop.  It's distended, not hard but squishy.  I have purchased Bragg ACV which I added to the water and I also gave her a bit of olive oil (filled the back of my finger nail, yes she is that tiny) and she took that.  I also got the Poly-Vi-Sol vitamins which I gave her a tiny drop.  I have been massaging the crop down, though what I have read says to massage up to get her to vomit but the chance of dying seems quite high.  

Time will tell.  I would really like to see her go to the bathroom and venture to the water by herself instead of my forcing her to drink.  

I do have to leave for a few hours today.  Hoping she is better when I get home.