Hi, welcome to BYC! 
Sorry to hear you and your neighbor are both having issues.
All questions that follow are in attempt to help and NO judgement for any answers... Please know this is a friendly questioning. 
You say last 9 months... when and where did you get your birds and at what age where they? How many in how much space? Did your neighbor get their's at the same place or time? How old are your birds now? What do you feed including treats and supplement? To be honest what I read says you might be killing them with kindness.. minerals specifically can be VERY deadly when out of whack.
Fresh veggies doesn't benefit much except enrichment.
Did you have a fecal float to make sure you were treating for the RIGHT worms, IF you even needed to? ($25 at my vet) Worming is poison can be very hard on the system, especially if they are already having an issue that isn't worm related.
Over 9 months... indicates it is NOT weather related, though it could have started out that way. Please tell how far apart are these birds passing? Also where are you located? When they lay down, have you got them back up to walk... or where do they lay down at? Do they stay there until they pass?
Skinny breast bones, seems only relevant to me if you know what they are like before that.
But it's an area I'm still learning in. When you start to see them get lethargic, is time for immediate action as things happen so fast with chickens and they HIDE anything just as long as they can so they don't become easy targets for predators and even their own flock.
What that immediate action is though, can be so variable. Almost always making sure they are getting fluids. Sometimes with electrolytes or vitamins added in. They won't starve to death, but dehydration is deadly fast. So I think that is most important. Which leads me to the next question... was their appetite gone when they did lay down?
Info to help facilitate necropsy...
https://www.backyardchickens.com/threads/how-to-send-a-bird-for-a-necropsy-pictures.799747/
https://www.aphis.usda.gov/animal_health/nahln/downloads/all_nahln_lab_list.pdf
I believe on the live you bird you might be able to do a gram stain (float) to tell you if their is a bacterial infection and which type would be the correct antiboitic, gram positive or negative... this again is another place I am still learning...


Sorry to hear you and your neighbor are both having issues.


You say last 9 months... when and where did you get your birds and at what age where they? How many in how much space? Did your neighbor get their's at the same place or time? How old are your birds now? What do you feed including treats and supplement? To be honest what I read says you might be killing them with kindness.. minerals specifically can be VERY deadly when out of whack.

Did you have a fecal float to make sure you were treating for the RIGHT worms, IF you even needed to? ($25 at my vet) Worming is poison can be very hard on the system, especially if they are already having an issue that isn't worm related.
Over 9 months... indicates it is NOT weather related, though it could have started out that way. Please tell how far apart are these birds passing? Also where are you located? When they lay down, have you got them back up to walk... or where do they lay down at? Do they stay there until they pass?
Skinny breast bones, seems only relevant to me if you know what they are like before that.


Where? I was told $40 at UC Davis for 1 bird, last season? It did used to be free for individuals but not anymore. And they did provide their commercial FED EX (only shipper of dead birds I think) shipping account to reduce my cost of shipping and said they would bill me afterwards.In California, necropsies are only $20 for two chickens.
Info to help facilitate necropsy...
https://www.backyardchickens.com/threads/how-to-send-a-bird-for-a-necropsy-pictures.799747/
https://www.aphis.usda.gov/animal_health/nahln/downloads/all_nahln_lab_list.pdf
I believe on the live you bird you might be able to do a gram stain (float) to tell you if their is a bacterial infection and which type would be the correct antiboitic, gram positive or negative... this again is another place I am still learning...
