I see. Yes, knowing your location is helpful.
Does the pet store have grit for pet birds like Parakeets or Parrots? You can use that.
It's very hard to know, but from some of the symptoms you describe, I would treat for Coccidiosis. Can you get some Amprolium or Sulfa Drugs. The pet store should have something to treat them with. Probably something labeled for pigeons.
They need access to food and water all day, so leave them enough food in their cage.
The one that has crop problems if it isn't pooping, then separate it out with water only for the day. Massage the crop and see if you can get that moving.