Black streaks on fins could be ammonia burns that are healing. Get ammonia
to 0 (also get your own test-kits if you can).

Goldie being nudged? hmm sounds like your goldie could be egg bound possibly.
Can you get hold of any medicated food - its possible that might help.
Try salting the tank (aquarium salt only). 1 table spoon per 3-5 gallons or
so, dissolve then add. See if goldie perks up after a few hours.

Anyone else got any suggestions?