How long after stress will they lay again?

I have 30 layers that slowly stopped laying this summer (it was about 9 eggs a day). THEN i introduced 8 layers, THEN a couple got sick (may have been sick before the intro), THEN NO eggs, THEN meds, and so a lot of stress and everyone is better, but no eggs. I also made the mistake of locking them in for 3 days (I was sure they were all laying out side the coop) so they just stopped altogether. I am not sure what was the actual cause of the egg stopping, but if it was just the stress, how long does it usually take before they start again? I know that the illness they picked up MAY cause a lifetime egg decrease (in which case I will just start over) so I am curious how long I should wait to see if they start again? They will have lights in their coop this winter and should lay all winter. Oh, and they are only 10-18 months, so they aren't too old to be laying or anything.
Thanks!

 

it's been at least 2 weeks. I may have thrown them into a molt. My ladies actually look great right now, but there are a lot of feathers laying around. some look fluffy, but the feathers dont pull out. How long do they stop laying to molt? Do some molt and not have bare spots? I was actually just noticing how they all look really nice and feather-y right now, but then I noticed feathers in the coop. Lets just hope its that. Good luck to you too!