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This is probably Sinningia Ozark Coral Freckles. I put it in a aquarium with artificial light on from 8:00am to 0:00am. The distance to light is about 20cm.
The young leaves were fine until they grew bigger and I found yellow spots within their leaves. I also spotted 2 tiny red dot things ( tiny, like dust ) on the leaves. I touched one of the red dots with a tool and it didn't move; I picked it out. I don't think they are red mites.
Any clues as to what is causing the yellowing?