When could I expect egg laying to start?

[rosemarythyme]

Not what you're asking, but electrolytes are not intended for daily use so I'd discontinue that and save it strictly for times when they need help with stress (i.e. a heat wave, a big shake up in their set up).

As far as signals that they're close to laying, I'd be looking for red, swollen combs, squatting, and exploration and messing around in nest boxes. Of what I can see in the photo, one of the red birds still has a pale comb compared to the other.

 

[Pukkits]

We got our 8 new orpingtons (3 lavender and 5 chocolate) in late February. A week ago we got our first little eggs. I'm not sure which ones or how many are laying. Their little eggs are so cute! We weren't expecting any eggs for a few more weeks.

I'd not worry about not laying yet. Most birds take their time, as they've got lots of growing to do to be able to healthily lay eggs. It's a lot to make from such small bodies! If it were me, I'd add crushed oyster shells free choice to your birds diet. It won't make them lay any faster, but it will help them maintain enough calcium to have strong egg shells and healthy amounts of calcium in their body. You don't need to measure, just set up a dish for them to take some as they wish.