My baby pigeon has black feathers & white pimples. Is it sick?

This is most likely pigeon pox. I would just leave it alone. There is no cure or treatment. In some cases it will resolve on it's own. It can be transmitted to your other birds. There is a vaccine and it is recommended.

18 days old is still a bit too young for a pigeon to be on its own, so the parents should be still caring for it. It's possible that the other baby is ill, or the parents ARE still caring for it and you just aren't catching them in the action. If you feel the baby is truly sick, injured, or not being cared for by its parents, then seeking help from a local wildlife rehab center is best. Do not attempt to move the baby or care for it yourself as it could still very well be cared for by the parents.

I would be very careful about cutting it off as there are a few skin infections that birds get which could do damge to the skin if cut. I would persevere with bathing it, and if it will not come away I would have an avian vet look at it as it is likely an infection that needs treatment.

This looks like Pigeon pox, some birds recover from the disease spontaneously others don't but there is no treatment for it (not dangerous to humans). Pigeon pox is a viral disease to which pigeons are susceptible. Pigeon pox is caused by a virus that is spread by mosquitoes and dirty water but not in droppings. The disease causes pox scabs to form around the bird's face, mouth and feet.

Thanks for using Petco Pet Education Center, formerly Petcoach! This may be due to something not ideal in her nutrition. This may also be due to her being sick as she is also very weak. This is something that can be due to a number of reasons but for sure warrants a veterinary evaluation for further assessment and treatment. I recommend you consider going to your veterinarian for further assessment. They may be able to check for these possibilities and treat accordingly. Best of luck!

Make sure there is nothing caught around the toe that could be causing constriction, if so remove it. It looks like the claw could be infected so you would need to take the pigeon to the vet and clean the toe with chlorhexidine whilst administering antibiotics such as baytril or terramycin.

It looks like the pigeon's ear may be a bit inflamed or there is some sort of growth/infection present. If they are wild birds, it would be best to contact a local wildlife rescue or animal control in your area so they can safely capture, examine, and treat the birds before releasing them back into the wild.