Chick breathing heavy and underdeveloped.

I received 7, day old bantam chicks on Mar 24th. Three Rose Combs, three sebrights, and one Old English. One of the Sebrights died the day after arrival. A second sebright had pasty butt which I cleaned and appears to be OK in that area. I then treated the little flock with tetramycin for a week removing any grit from their diet. However, that littl, second sebright continues to breathe heavier and more frequently than the rest of the flock and appears to be at least a week or more behind the others in feather growth and size. It has a healthy appetite, drinks plenty of water and is active. It does appear to be cold at times because it seeks to get under the wing or body of the others. Four of the 6 are now outside and doing well here in South Florida. I have kept the remaining chick and a healthy companion inside under the lamp until such time as the little one feathers out a little better. The other chicks are fine. This one appears to be as active as the other ones but behind in its development and still breathes rapidly and heavy. Any idea what might be wrong and what I can do about it?

I too have a aracana that was the smallest of my batch, the only one with pasty butt and her feathers are weak coming in and she seems to be just not quite well....being the smaller it looks as though shes losing her feathers thinner around the neck and looks like some pecking going on...still active...but just not as well...she just pooped non formed...while the other girls are firm poopers....im going to start her on a little extra protein with seperation for feeding so she gets sole ownership of the much needed weight gain...then recoop for the the day and see how much pecking etc goes on....my coop is 67 at night in the main area with the roost with a heat lamp at 75...all the girls are spread in the mid to cool zone their roost area where I try and keep it a little warmer for them should they need it....now i just need to calculate out the dosage of tetramycin for her only...any ideas? she only does heavy breathing when she's been rolling in the shavings as they all have been doing event though they have some dirt sand bowl for dusting....

in looking for smaller dosage etc for meds for poultry I found this link....

https://sites.google.com/a/poultrypedia.com/poultrypedia/medicine-chart



the medicine chart for poultry etc....good info on dosages and breakdowns...I iwill be printing this out for reference!!!!

https://sites.google.com/a/poultrypedia.com/poultrypedia/medicine-chart



this might help for future references....I have my one sick chick......needed to get a little better dosage for her...she is now in isolation....eating egg yolk pepper and cornmeal and electolytes in her water...going to see if she will take more water...
if not its syringe time..