I've been making a set of white "marking" tattoos to go over my feline skin set, and it's mostly been working fine, but I've noticed that a few specific tattoo areas (lower arms, and left leg, as far as I've noticed) are showing up noticeably darker than the others. They all look the same in Sims 4 Studio, and all of them are being created exactly the same way in Clip Studio so there should be no visual difference.

Brown areas are the base skin, white/grey are the marking overlays. I'm using a separate package file for each area so the markings on each arm/leg/etc. can be mixed and matched. Markings should be overlapping seamlessly at the upper leg there, and they do with every other slot I'm using (second image below is the same problem in the lower arm slot, over another hand marking in the not-broken upper arm slot).
Is this just a bug or a known thing that happens, or is something weird going on? I can probably just adjust some levels for the problem slots to compensate if needed, but I'd rather fix it on the technical side if I can.

Please upload the packages so I can take a look.

uploaded them to the main post.

You need to change the Composition Method to 1 for the parts that are showing up dark.

That did it, thank you!