3 months without eggs

Short question: my chickens haven't laid eggs in a very long time, and I am not sure why?

This is somewhat of a long post because it seems that there have been many events that have occurred which alone could be the cause of my issues, but due to the complexity of them, I don't know which it is, or which is most likely.

History with relevant events (I am guessing on some of this, but this is approximately the history):

- Had 3 chickens (1.5 year old, 1 orp mix and 2 americana) and 2 ducks (1.5 year old). The ducks have laid every day forever, even through the winter. The two americanas lay an egg each every other day, while the orp mix lays daily (so 3-5 eggs/day total). Previously fed the nutrena layer. They have a tall 4x6 (or so) coop with a 4x16 enclosed run with an additional 80 or so sqft to play in outside of this area (long story, but they were free ranged and now just have a fenced in yard). Chickens roost and the ducks have a ramp and then sleep on floor under chickens.

- May switch food (frin nutrena) to a local SC company, OMC. The orp is broody for a bit, but she does that.

- June was crazy hot.

- mid-June orp mix went broody again, but only for a week (I bet the snake made her move) and one of the ducks molted, so was only getting one duck egg a day

- Late June got a pair of 3 month old lavender orps who got put in a space under raised coop. The following week one had been eaten by a rat snake (snake relocated and coop secured, like really really secured)

- July 4 got four young orps for the lone lavender orp who wasn't ready for the big flock (ducks were mean), but needed company. They all continued to live under the coop until mid-September

- July (hot) I still wasn't getting eggs. I put out some old eggs in the nest box and nothing ate them, and also had a minnow trap with an egg and never caught anything.

- August, still no eggs, but at end of August all the older chickens started molting and one of the ducks. Checked again for snakes and found nothing.

- September (hot and wet), still no eggs, young chicken flock got introduced and does very well, definitely bottom of pecking order. The older chickens feathers are coming back in and I expected eggs to start showing back up.

- October (crazy wet with 2 feet of rain, etc) still no eggs. The older chickens looked skinnier and I found out a friend nearby had coccidiosis (based on bloody stool and two chickens died; she treated and all are well). No stools with blood. October 13 noticed one of the older girls was wobbly, so she is being isolated during the day. Tonight, October 15, Corid is arriving and I am going to treat the whole flock (my reasoning is that it has been hot and wet and they are looking skinny).

Possible options that I can see:
disease
heat
shorter days
stress
diet

I can't think of what is stressing them, and the new chickens seem to be thriving (really really plump fluffy orps). The shorter days were never an issue for the ducks and they aren't laying. So what could I be missing or what seems likely, and/or a good course of action?

Thanks ahead of time and sorry for all the background.