Chick with Distended Belly?

[Happy Henny]

I have a chick that is being raised by a polish hen outside in her coop. I picked him up today and washed some poop off his stomach and his stomach seems to be lumpy and distended while his vent is swollen and red. He is active and happy as ever and eats and drinks his fill. (pics attached of butt) Also, theres a fluid filled bubble right above his crop, under his neck. It's not inflamed or red and it is clear, see through liquid inside. He doesn't seem affected by it. I've heard these can appear on chicks but dont affect them and eventually reabsorb. Does his rump look normal? If not, what could be affecting him? TIA

 

[Wyorp Rock]

Also, theres a fluid filled bubble right above his crop, under his neck

his stomach and his stomach seems to be lumpy and distended while his vent is swollen and red

active and happy as ever and eats and drinks his fill

Do you have a photo of the bubble above the crop? It has fluid in it or possibly air?

I too would be concerned about the distended abdomen and even the discolored area. It could be the first signs of infection of the Yolk Sac (Omphalitis) but since he's eating/drinking fine and seems o.k. that's puzzling.
I would continue to keep him cleaned up, watch for symptoms of lethargy, going off feed, etc. The vent is swollen too, you can put a little coconut oil, vaseline or anti-inflammatory cream on that to see if it helps. A daily soak in a warm epsom salts bath may be beneficial as well.

Does he seem to strain when pooping?