they make UV lights you can buy made for like plants and what not. I would assume they're somewhat expensive but definitely worth it if you barely get any sunlight
I was watching YouTube videos on this and in the comments somebody said it's caused by air bubble so maybe it's a factory defect. I also saw a video a while ago having to do with WD-40 only reason I didn't try it is because I'm lazy and keep forgetting to get it. I did try baby powder on mine...