What is this on the tincture jar??

I'm new to tinctures and I just looked at one that's been sitting for just over 3 weeks. It is a passionflower tincture made with 100 proof vodka. I only noticed with a flashlight but something is growing on the inside of the glass. Nothing is growing on the top I opened the jar to check. It's not on the herb or floating just on the glass. Any ideas? Is it mold?
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