Hi, is your oranda still doing okay? I'm not a goldfish person, having never kept them, but it almost sounds like an adjustment period he went through. Goodluck!

the black spots could have been subdermal hematomas (spelling?) which are very bad and usual the last stages of an infection. literally internal bleeding. usually this condition starts with frayed fins or fin rot which is a sign of external infection. if your fish's fins are all perfect, likely there was no internal infection. the black spot might just be natural. black in most breeds is a transitional color. your orange fish was all black as a baby the turned orange from the belly up as it aged. sometimes for no apparent reason a little of the black comes back from time to time. usually on the fins. i notice it more in the spring than any other time. it might be influenced by environmental changes such as temperature. it usually only lasts a few weeks and has nothing to do with health. it is hard to tell which spots your fish has from the description.

as for your goldfish, it might be sick, or maybe might have been bullied by the moore and unable to feed but still healthy. another possibility is your fish might be a female the moor a male and they may have spawned and your fish may have been tired and abused.

the feces are troubling. below you will find a feces description and what they might mean.

Healthy Feces - Should be the color of the food they consume. Short and somewhat chunky in appearance.

Thin Floating Feces - Long and thin, the color of the food they have consumed. Typically poor diet related.

Thick Floating Feces - Long and thick, the color of the food they have consumed. Typically a sign of overfeeding, can be poor diet related as well.

Thin, White Floating Feces - White and stringy in appearance, it is usually a sign of an internal bacterial infection.

Long, Thick Chunky in Spots with Mucous casing, Floating Feces - Typically the color of the food they have consumed, with large areas of what appears to be air bubbles in a mucous casing. This is typically being caused by the food fermenting. Soak food before feeding.

Diarrhea - You will notice a brown tinge to the water. This is typically a sign of infection.

Clear Long Feces - Re-absorbed eggs.

my guess, tiered stressed and hungry becuse of the moore, or an internal infection.

if the fish appears to be recovered or recovering you may not need medication. if the spots are still there look for a medication for dropsy and fin rot and follow the instructions. if it is on the up and up, use aquarium salt if you are already not doing so. if it is somewhere in between, use salt but double the amount recommended on the package for the next month then step back to the regular dosage. do a google search for salt "treatment" and "goldfish" for more info.

good luck.