25 healthy chickens laying 15 eggs a day. Why?

Please help. I have 25 chickens (2 Buff Orpingtons, 2 Barred Rock, 2 Silver Laced Wyandotte, the rest are red sex-link). All were good layers last year. This is my first spring with adult chickens. We use a chicken tractor and free-range so it is hard to lock them in. I catch them in the barn sometimes. Last week I found 2 old nests in the hay loft and got rid of the old eggs and rearranged the hay so there aren't any private holes for them to want to lay in. This morning I figured a way to keep them locked in all day. I got 15 eggs from 25 hens. I have been getting about this many every day for about 3 weeks. There were two days in early March when I got 24 and 21 eggs, which is the amount I expect. I know 1 of the Orpingtons was broody, so I put her in a separate pen for a couple days. I haven't seen her sit on the nest all day since, but I don't know if she is laying. None of them appear sick or unhappy.

How do I figure out who is laying and who is not? How do I jumpstart them all so they will lay? I plan to keep them confined tomorrow and keep tomorrow's eggs separate to see how many light ones I get and how dark ones from the red sex-links. But still how will I know who is laying? Will it encourage them to lay just by not letting them out until after laying time is over? Will being cooped up all day stress them and give me fewer eggs?

I just got an egg at 6:15 PM. I have never gotten one that late before. Is it from being locked up all day? So today I got 16 eggs from 25 hens.

I give them commercial layer's feed and a treat of up to 2 or 3 heals of bread a day. No more than that. I was giving them some scratch over the cold months, but have stopped that since it is nice out.

Please help, I need more eggs.

Eggs will be laid at all times of day. It seems like they all come early only because since they come at 25+ hour intervals, they will always be later each day.
That routine causes the bulk to come right after dawn. Those are the ones that would have come during the night. The rest will come later and later each day.

If you need 22-25 eggs per day from 25 hens, keep leghorns, ISA or Hyline hybrids - not orps, rocks or wyandottes.
Those breeds lay around 170-200 eggs a year so they are right on their target for their breed expectations.

If you think you're concerned now, wait till they all molt this autumn and you get few or none.
They laid well last year because they were pullets.
They can continue to lay well (170+) for several years. They will take an autumn/winter break every year though.

Thank you for your response. I thought red sex-links, of which I have 19, were supposed to really produce.

They do lay well but not likely significantly more than their parentage.
Red Sex-Links are the result of various crosses. White Rocks with the silver factor are crossed with a New Hampshire male to produce the Golden Comet.
Silver Laced Wyandotte crossed with New Hampshire gives the Cinnamon Queen.
Two other crosses are obtained with Rhode Island White x Rhode Island Red, and Delaware x Production Red. These two crosses are simply called Red Sex-Links. Males hatch out white and, depending on the cross, feather out to pure white or with some black feathering. Females hatch out buff or red also depending on cross, and they feather out in one of three ways.

The RIR and Production Red contribute those great egg production genes.

I mentioned leghorns but RIRs lay nearly as well.

Here are your super laying hybrids. Still they will only do so for about 18 months.
http://www.hyline.com/
https://townlinehatchery.com/product/isa-browns/

On the other hand, I have a 7 year old ameraucana that continues to lay about 4 eggs a week except from September - December when she takes a break.