Puffy Welsummer not laying eggs

[HoundsHarvestFarm]

So we have 2 Welsummers a little over 1 year old. One tends to always be puffy and because we have never gotten 2 dark eggs on a single day I have deduced she has never laid. Her poops are loose but not complete mush and I am starting to think this is not ever going to resolve. Her comb is both lighter and smaller then her sister. I do have her finally in her own space as I try specifically to watch her and verify she is not laying. She does move around with the flock when she was with the group but also tended to stand still longer and my wife is telling me she has been like that for 9 months. Thoughts, ideas on medication for her?
All of the ladies got a antibiotics treatment last summer when we had a respiratory illness that killed a duck.

 

[Goosebaby]

My guess is that the illness is still present and she has it chronically. It might be a good idea to get her looked at and tested, if the others have it stress could bring it out whatever it is “bacterial, viral, mycoplasma” at any point.