Black mark on the outside of the Onahole

[HibikiLove]

So I bought this Onahole a couple of months ago (Around 5-ish) and have been using it a lot ever since. I ensure to always clean it after each use to ensure it's ready for the next one. However, I noticed today when I checked it that I saw this strange black mark on the outside of the onahole. I wasn't sure what it was and I'm not sure how I'm suppose to get rid of it. Any ideas anyone?

[HibikiLove]

I'm using this video as reference: (https://www.youtube.com/watch?v=lYlc30vojRs) and referring to 9:18, he talks about black spots and any weird odour, he says to discontinue it. However, my black mark is more of a line instead of a black spot. Would it be considered that?

[AkaiHebi]

Could be mold. Try treating it with a hydrogen peroxide solution

[HibikiLove]

Could be mold. Try treating it with a hydrogen peroxide solution

So I was reading the part where you were talking about using Hydrogen Peroxide: "If you notice black/white mold spots developing inside, use 3% hydrogen peroxide for 15-30 minutes at least once per week, make it as dry as possible..."

So I was wondering how would you do it? Do you dab it with the Hydrogen peroxide or douse in it. If I was to do it 15-30 minutes through dabbing it, would I have to continuously ensure that it has Hydrogen peroxide for the full duration?

[AkaiHebi]

I'd simply spray it on all the surface and let it rest for the duration, then washing with water and soap and drying