8 week old that is not gaining weight

[my beautiful girls]

I have a black australorp that has only gained 32 grams this week and she is very thin. she is active and eats and drinks. prior to this she has been gaining 100 grams a week. Her sister weighs almost 200 grams more than her. She does seem to be more skittish than the others, some of her neck feathers are still downy while everyone else has feathered in. Her keel is very prominent. her vent looks good but her hip bones are very pronounced. crop is good. the 4 get along and no one is bullying. They were all tested for cocci, salmonella and clostridium perfringens. all were negative. sometimes her poops have a clear urate around the solid part. Not consistent. I am going to put nutri drench in their water tomorrow. What else can I do to help her gain some weight? she is so thin. Thank you in advance.

 

[GlicksChicks]

Maybe try giving them some boiled eggs and/or some meal worms for protein to help bulk up. Try to target that chick the most for feeding the protein treats to.

There is also a chance that she is just growing different as well. Some chickens lag behind, either for genetics or illness. Since you tested yours, I would say for genetics.