I would suggest not using water to clean an occupied nest box, since moisture increases the chance of mold developing. You can use a scraper to knock most of the poop off the nestbox walls, and it's OK if there's some poop residue. The nest should be washed thoroughly when the breeding period is over and the nest is no longer being used, so it will be clean and dry when it's needed again.

The babies start eating less sometime around the age of three to four weeks, before they fledge. At this point they aren't growing very fast and their feathers are mostly complete, so they don't need as many calories and nutrients. But they're getting ready to fledge and a big heavy crop would make it difficult to fly, so that's another reason to eat less.

Sorry you found mold. Im not sure there is much you can do about it because the birds are using it. I agree, you should keep it dry for the mold to stop growing. Mold grows on wet wood.

thanks. I just was very surprised as I did everything as before and never had a problem.
How about people spraying water inside the box for humidity??? I never do it, but I sometimes spray my birds when they sit on top of the breeding cage. I thought it might not be very humid in the winter with heater working.

I actually sprayed the walls on my nest box in breeding and I didn't have problems. Maybe mold grows when the pine shavings get wet.

Eggs need some humidity in order to hatch properly so spraying the walls of the nestbox can help if the humidity is low at hatch time. But most of the time it isn't desirable. If your humidity is very low right now, hanging up a wet towel in the room or setting out a shallow bowl of water will help add some humidity without getting the nestbox wet.

If the babies have very wet droppings it can lead to mold growing in the nest, but this usually isn't a problem. Sometimes the shavings themselves were contaminated in advance because they got wet long before you bought them. They should look nice and clean with a "fresh wood" color. If they're dark and discolored before you even take them out of the bag then something went wrong and you shouldn't use them.

what is it like to have more than 10 birds? I will have 11 when the new babies fledge.

How long do you think my birds need to sleep at night at this time?

Having a lot of birds can be chaotic. If you keep all the babies, you'll have a problem when they grow up and want to breed with each other. Birds have no qualms about incest, but it's not a good practice to let siblings make babies with each other because there's a high risk of birth defects in the chicks.

When my birds are finishing up a clutch I can discourage them from starting another one by simply making the nights seem an hour longer than what they're used to.

Yesterday I broke the nest box when I was cleaning it. Accidentally forced the lid open way too much when I was shaking out bedding. Wood on the lid chipped near pins connecting lid and the box. I can still carefully use it but need to be careful not to get wooden particles into chicks' eyes (this is my concern). It's not that simple now to open the lid to look in.
Are all of them pied?

mold started growing again in the box. Bedding lasted only 2 days. Bedding itself looks totally fine in the bag

Bella got caught foraging in the cupboard where seeds are getting sprouted Bella is my special chick. She has a relationship with me since the time I handfed her. She always flies to my head.
whats your opinion - I dropped glass dropper in the bottle of vinegar, it can be seen on the pic. No way to get it out unless I empty the bottle that is a lot of hassle for me. Is it OK to use vinegar with dropper in the bottle? Would dropper contaminate vinegar? It was a clean dropper I used to measure vinegar only but outside of it wasn't sterile of course