Goldfish Has 2 Black Scales

My lovely goldfish (who just went through a color change from its baby brown color to white/gold/orange) has 2 black scales. The ammonia level is at a perfect 0 and its behavior is normal (still swimming around, eating, alert), so I don't believe it has an ammonia burn or a fungus. As I said, it is just two single black scales that won't even show up in a picture. The best way to describe them is two individual black scales on the bottom of its body. One scale is just behind something called the pelvic fin and the other is farther back, they do not touch.
I just did a 50-60% water change and cleared the filter just in case (also it was time anyway) and I have read that aquarium salt can help in situations like this.
Is there anything wrong with it, or is it just part of its color change?

Any chance of a picture of the fish?
If the pictures are too big for the website, set the camera's resolution to its lowest setting and take some more. The lower resolution will make the images smaller and they should fit on this website. Check the pictures on your pc and find a couple that are clear and show the problem, and post them here. Make sure you turn the camera's resolution back up after you have taken the pics otherwise all your pictures will be small.

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It's probably just colour and nothing to worry about but a picture will help confirm that.

You have already check the ammonia, but check the nitrite, nitrate and pH levels to make sure they are good.

Fungus is white not black.

Don't bother adding salt just yet. Just do a 75% water change and gravel clean the substrate every day for a week and monitor the fish. Make sure nay new water is free of chlorine/ chloramine before it's added to the tank.

Here are the best pictures I could get, the problem is not with uploading them, but rather with the scales being small (and apparently quite shiny) and the fish moving haha. It just looks like a small black dot. I went ahead and ran those tests, high range ph (good for goldfish) was a perfect 7.4, nitrite was 0, and nitrate was also 0.

Additional information:
*These scales were noticed last night.
*I recently bought filter sponges as I was advised to. They were definitely the wrong size, even after cutting (too thick??), but I cut them thinner and essentially stacked them in the filter next to my current filter system after it had been thouroughly rinsed in removed tank water. The current filter situation is a replaceable filter cartridge (they will stay together for a while as I was advised). My filter is set up to have a space in the back, then the filter cartridge, then a black plastic sheet with holes it in (I assume this is for some kind of algal growth filtration, honestly I have no idea but it tends to allow things to grow in the holes (side note, should I clean this out or let it be established?)). I also washed out the inside of the filter box thingy today which was apparently long overdue and will definitely be happening more regularly.
One further question, can the sponge be the only filtering thing, or does my filter also need something else with the sponge?

I wouldn't worry about it. The dark spot near the tail looks like it is close to the fish's butt and my be its butt. No idea where the other spot is but if the fish is eating and swimming well, don't worry about it.

If the spots get bigger or spread, then post more pictures that clearly show the dark scales and we can investigate it further.

This fish actually still has a lot of adolescent color and will probably continue to change color some. I would suggest feeding him a high quality food like Omega One or New Life Spectrum to enhance color. These products really do make a difference. Your fish looks very healthy to me.

Okay, thanks to both of you!