I'm guessing it copper oxidation maybe? Gold plating is usually done with a copper layer first then the gold is plated to that. Maybe clean your keyboard with rubbing alcohol after each use IDK.

That's definitely brass/copper corrosion. Probably brought on by exposure to moisture and whatever else your fingers leave behind on the surface.

From what I see the manufacturer's website claims that they're "electroplated" but does not go as far as to specify that they are actually gold. So, are you sure about that? The plating is probably brass, or certainly at least contains copper.

Someone never having seen copper corrosion got me fucked up. It's definitely corroded copper, the "rose gold plating" is trash.

Not really an easy fix for it, you could clean all your keys really well and seal with clear epoxy or just embrace the new aesthetic. Oxidation like that is self-sealing, it'll stop once the whole surface is covered and imo looks pretty neat once you brush it smooth

That looks like corrosion to me too. You might be able to clean it off, but it'll probably come back unless you seal the copper or wipe them all off regularly.

I had no idea a keyboard like that existed and now I kind of want one. The only thing that's saving my wallet is that they don't actually seem to offer one that's styled like a retro typewriter. I don't want lilac or matcha green block colours. If they had a black one with brass and off-whites like a 1920s Underwood typewriter I'd have snap bought it.

This is corrosion of the copper in the brass by oxygen. Clean with mild acid like vinegar.

As people have said it's likely corrosion. More specifically, verdigris. It's the same sort of corrosion you see on the nosebridge of glasses. It's caused by the oils on your skin reacting with the bare metal of the keycaps. There isn't really a solution to stop it, apart from putting a clear coat over the metal.

Looks like copper corrosion, I'm guessing its gold plated copper, and the oils/sweat in your fingers is corroding the copper underneight?

Definitely copper corrosion. Rose gold is an alloy of copper and gold, and since it's a mechanical keyboard, I doubt they're springing for super high quality stuff, so it's probably more copper than gold. As another said, white vinegar with a few tablespoons of salt should remove the corossion, but I'm not sure how the rest of the keycap will hold up.

To add to what others are saying:

You can clean them, but the corrosion will come back over time.

Verdigris is mildly toxic by the way. This metal, whatever it is, seems like a bad choice for keycap material. Might want to wash hands after use.

Checked the board online (https://www.eweadn.com/products/eweadn-v20-typewriter-keyboard)

$40 for a full keyboard with "electroplated" keycaps. Others are right that vinegar will clean them right off but I suspect there's not gonna be much of anything left after it goes in for a soak.

Others may have better ideas on what can be done to preserve them at this point, but for something like that which likely has a very thin coat of easily oxidized metal the best maintenance is gonna be preventative. IDK what the best option is but I'd consider hitting it with a super thin coat or two of a drying oil like tung oil upon receipt. Wipe each key down with an oily rag, then wipe it off with a dry rag like you made a mistake. Allow 1-2 weeks for the tung oil to dry (plasticize). Clean all keys and reapply oil at the first sign of oxidization on any keycap.

Looks like finger jam. You can tell it's not lung butter, or else it'd be yellow.

One practical tip on top of the corrosion answers: pull the caps off before cleaning, if you can. A damp cotton swab gets into that rim seam much better than wiping the board in place, and it keeps liquid away from the switches. Dry them fully before putting them back, or the buildup just comes back faster in that seam.