8 mo old hens never started laying

Hi - I've been reading everything I could find to try and answer my question but haven't seen quite the same kind of question as what I'm asking - hoping you can help.

I got a total of six hens from someone locally and they were about 5 months old in July when I got them and I was told they would begin laying in about a month. They have never started laying. The woman I got them from said that the hens she kept from the same broods have all started laying and that she's heard from several other people who got hens from the same brood that they are laying. I've only been doing chickens since March - so maybe this is normal, but I don't think so. Help! I have no idea what is going on as they are all about 8 months old now, I'm concerned that they may be sick or perhaps I'm doing something wrong. Details below:

Previous to this I had 5 Speckled Sussexes and they did great (1-4 eggs a week) in the same run and coop with the same kind and amount of feed.

Current Breeds:
2 orpingtons, 1 americauna, 1 auracana, 1 maran, 1 barnevelder - got the first 3 and second 3 about 1 month apart, but all from the same place with a great reputation.

Feed:
Free access to pellets and water, apprx 2 cups crumble, 2 cups scratch daily, oyster shells, kitchen scraps (no salt, potatoes, etc and all the other list of bad stuff you're not supposed to give them) and weeds/grass/dandelions (what grows in the backyard). They are not free range due to predator concerns. We used to keep a flock block for the speckleds to help with their hen pecking problem - none of the new hens like it and they also can't seem to figure out how to drink from the hanging waterer that has a nipple - so their water is in a traditional waterer.

Health:
When I got them I wormed them as a matter of course, particularly as there was a 2 week overlap with my Speckeleds - no signs of worms. I put lice powder in with the bedding regularly and I haven't seen any signs of lice or mites. Their poo looks normal. I thought that the Maran might have had some weight loss, but it's been hard to tell since they are all kind of skiddish and I try not to stress them out by catching them. Ameracauna seems like a bantam - she's grown a little since we got her, but not much. I wormed them again in the last week of September, and then last Wednesday put them on some poultry antibiotics (got it at my farm store, can't remember what it was - yellow powder?) They've been on the antibiotics for 1 week +1 day.

Behavior:
They don't seem to have any odd behavior. Not too much sleeping or over preening or listless. They all seem to eat and drink just fine.

Location:
We have a fully fenced run (about 15'x15' square and 7' tall)with a coop inside (protecting from raccoons). The run gets cleaned weekly and we use straw as a floor. The coop is one we built and that was previously used by our Speckleds. It is about 4' long and 2.5' wide. Has 2 nest boxes and a roost. We clean it weekly too and it has shavings in it for bedding. They roost every night with one hen keeping watch on the door down below. We keep the coop open at all times since the run is protected - that way they can get up and put themselves to bed whenever they want. We've had plastic eggs in the nest boxes for 2 weeks.

I heard that sometimes hens won't lay where previous hens have and that they will hide their eggs - there's no place for them to hide their eggs that we wouldn't have seen. Yesterday I put the large animal carrier that we use to transport them into the run and put shavings and hay in it to give them an alternate safe place for laying - they knocked out most of the bedding and pooped in the carrier, but that's it.

Rodents:
We've caught a handful of rats outside the run, but none on the inside. This started when we had our Speckleds and we never saw any instances of broken eggs - it looked like they were going for the sweet flock block. Haven't caught anything in about 2.5 months.

I can't think of anything else. Any help would be greatly appreciated. Thanks!

 

Thanks all. They currently have free access to the layer pellets - I just mix the crumble into the scratch in addition to that. Regarding rats, I haven't seen any evidence and I've got hardware fabric buried 2' deep in the soil, so I'm not too concerned about tunnels. But I guess rats could still be getting in - I thought they tended to leave evidence though when they ate eggs? I haven't seen any shells or mess. I'm in Seattle and we're down to less sunlight for sure and it's down to the upper 40's at night. The reason I was discounting this is because others from the same hatching were already laying. I'm happy to be patient, but I was just worried that maybe they were sick and I was missing the signs? Or maybe something else?

Photos of the hens here: http://www.facebook.com/home.php?#!/TwoMoggiesFarm