A bunch of multi-colored dots suddenly appeared on my iPhone 6s' screen (stuck pixels? bug?)

I have an iPhone 6s, 32 GB, running iOS 15.1 for several months, and I've never seen any type of problem or defect. However, when using it this morning, I noticed a minuscule, cyan-colored dot on the middle of the screen, on a black background, which made me very weirded out. Seemed to be a scratch or dust on my protector at first, but after analyzing with more precision, it was clear that it really wasn't. It was on the display. Speculating that may be a bug, I restarted the device, just to find out that two more of the same type were standing together with the first one that appeared there. Restarted again, adjusted the luminosity to the max, and did a check using a dark grey background. With this technique, I managed to see a bunch of small pixel-things, assorted in red, blue, green, and yellow colors, scattered around the screen. Afraid that they might be dead pixels, I did a research for "dead pixel iphone", a generic term, but none of the results were similar to mine. According to the internet, dead pixels are pitch black and don't change depending on the tone of the image, which is not my case. What do you guys think about it? I assume that they are stuck pixels or an OS bug, but still not sure. The device's battery health dropped yesterday to 81 percent, this could be a factor?