Yellow stains on my Magic Keyboard and Magic Mouse

I previously contacted the Apple Care Hotline about this and it doesn't seem to lead anywhere satisfactory, so now I'm going public with this situation for all to know. This iMac that my employer purchased for company use is brand-spanking new (bought since February 12), and I only started using it since February 15. And about two weeks ago my Magic Mouse started to develop a yellowish stain on top of the centre where you perform scrolling actions. I tried to clean it with a damp cloth and even used alcohol wipes, but nothing seemed to work. And then about a week ago, my Magic Keyboard developed the same stains as well, and particularly on the Z key (even though I rarely use them compared to several other keys that didn't show any stains). Tried the same cleaning measures that I did with the mouse, and the result was all-the-same.

What the heck is going on?! I don't eat or drink anywhere near these devices, and I always keep my hands clean whenever using them. Even my own personal MacBook Pro's black keyboard, trackpad and Magic Mouse never developed these staining issues, and I've been using them for over 4 years! What gives, Apple?! These iMac devices are brand new, so how is it possible that such issues can occur this soon?

I've attached photos of said Magic Mouse and Keyboard with said yellow stains for everyone to see, to show that I'm not making this up. Have a look for yourselves.

I don't know what to make of this, and when I contacted the Apple Care Hotline they came to the conclusion that I should send this over to a service centre. The thing is, they explicitly said that they will NOT cover the costs involved and that I will have to pay for it myself. Apparently they don't consider it a manufacturing or product defect, and the senior representative continuously questioned my personal hygiene when using these devices. I've never felt so insulted and appalled by how Apple handled this situation! They don't even know what's the actual cause for these unremovable yellow stains, and yet they have the nerve to ask me to send them over without any assurance from their end!

Okay I'm done, and I do apologise if this post feels like a rant. I'm just frustrated over how this issue first came about, and how I've been treated by Apple. And if any Apple representatives are seeing this post and assume that I'm making this all up, below are the case numbers that pertain to my issue.

100779777875

100780683747

If anyone else has a trick or so that I can still give a go, please let me know. Cause I absolutely refuse to send these devices over to the service centre and pay for any costs involved, when Apple can't even provide a proper answer and won't even cover what is NOT a mere cosmetic issue!