Please need help about my calathea white star

[Holidaylover]

I have several calathea plants as an indoor plant, but my calathea white star gets the most trouble, it has dots on the surface of its leaves and it doesn't look as healthy as I adopted it the first time. I am sure it's not overwater or being exposed to the direct sunlight, and i put it together with other calathea I have. Could anyone tell me what went wrong? Thanks so much in advance. Greetings from holland.