meat spots and low numbers

I would say your hens are a little on the old side for good egg production. Egg production really starts to drop off after 2 years.

 

Yup, increases with age. Here you go:

http://www.thepoultrysite.com/publications/1/egg-quality-handbook/29/meat-spots

 

Yup, those girls are past their prime. You may consider retiring the 3.5 y.o. hens. The 2.5. y.o. hens may have another 6 months of good production in them, but egg quality is going to continue to deteriorate at their age. I consider culling when the girls reach 3 y.o. because they spend more time not laying than laying and the egg quality starts slipping a bit- shells start getting thinner/funky looking, meat/blood spots become more prevalent, whites get thinner, etc.

The reason for your slow down is probably light related mostly, but certainly is age related as well. My nearly 4 y.o. hens (Yeah, I considered culling but I love these old biddies so I am stuck with them) have not laid any eggs since molting this fall. Fortunately, my flock has birds from all age groups, so I am still getting eggs despite their hiatus.

Good luck.