Hello everyone, I have a few questions and concerns.

I have a 30x20x20 cm aquarium that's been in operation for two years. It's full of soft corals like GSP, mushroom, and zoa. Three days ago, I added two more SPS corals: Red Montipora Cap and another species, I'm not sure which, but they were sourced in Vietnam. I use a K7 mini light from 9 AM to 7 PM, and the tank temperature fluctuates between 27-30°C. Recently, I've noticed that some of my Red Montipora Cap have a slightly white area, but that spot still has polyps and is growing evenly. Does anyone know the reason?

And should I increase the UV light from 15%-20% between 12 PM and 4 PM?

Thank you everyone.