Trauma or slow spreading disease?

[MarinaR]

I have two hens that haven't laid an egg in 3 months. I had one other hen die last week from suspected Egg Yoke Peritonitis that was a terrible layer.
One of my non-layers was a consistent layer but had a bad foot injury about three months ago that took 2-3 weeks to heal but has not laid since.
My other non-layer never really started laying consistently. She laid sporadically but stopped laying around the same time as the one with the foot injury. Her sister died last week (she had major problems from the beginning of her sporadic laying career). Reliable breeder says this breed is her best layer.
I have two other hens who are very consistent layers and started laying before her much older coop mates (the sisters). Lastly, I have two new RTL hens that started laying the day after they arrived. My consistent layers took two days off due to the new birds and are back to consistently layng.‎ So I usually get 4 eggs a day out of 6 hens.
So question: my two non-layers are not laying due to slow spreading disease or trauma related? I can't be doing something terribly wrong as I do have a few consistent layers. I just don't understand what's going on the the oldest two (which are about 15months old by the way).

 

[MROO]

I have two hens that haven't laid an egg in 3 months. I had one other hen die last week from suspected Egg Yoke Peritonitis that was a terrible layer.
One of my non-layers was a consistent layer but had a bad foot injury about three months ago that took 2-3 weeks to heal but has not laid since.
My other non-layer never really started laying consistently. She laid sporadically but stopped laying around the same time as the one with the foot injury. Her sister died last week (she had major problems from the beginning of her sporadic laying career). Reliable breeder says this breed is her best layer.
I have two other hens who are very consistent layers and started laying before her much older coop mates (the sisters). Lastly, I have two new RTL hens that started laying the day after they arrived. My consistent layers took two days off due to the new birds and are back to consistently layng.‎ So I usually get 4 eggs a day out of 6 hens.
So question: my two non-layers are not laying due to slow spreading disease or trauma related? I can't be doing something terribly wrong as I do have a few consistent layers. I just don't understand what's going on the the oldest two (which are about 15months old by the way).

Have you checked for mites? Look closely under their bellies and around their vents for little critters, sores, nits and/or eggs. A bad mite infestation really taxes their systems. It can do a lot more damage than costing you eggs. It can kill them. Luckily, getting rid of them isn't usually expensive and is easy on the birds ... it just takes a lot of persistence to get rid of the little buggers!

 

[MarinaR]

Have you checked for mites? Look closely under their bellies and around their vents for little critters, sores, nits and/or eggs. A bad mite infestation really taxes their systems. It can do a lot more damage than costing you eggs. It can kill them. Luckily, getting rid of them isn't usually expensive and is easy on the birds ... it just takes a lot of persistence to get rid of the little buggers!

I thought of parasites so do check on a regular basis and I dewormed about a month ago. No evidence of parasites that i can see and their combs are red. And no laying for just two birds. I thought it would affect all of them or at least a few more.