@David-TP 

Hello David,

i wouldn´t say hot but warm? Yes it is warm. It´s also not under direct sunglight, and it developed on the same spot on two units both in different located in different rooms. I noticed only recently so i´m not sure how long it can be that way. Probably couple of weeks. I also didn´t notice any performance issues.

  @Harant  Same thing here on one unit. It is the main one and looks just like in your picture. I have 4 in total: One other unit has it, but about have as much as the main unit, while the other 2 have none off it. Sort of weird since I bought 3 of them at the same time in 2019 as a set. So why two have it in different degrees and one of them does not, feels a bit strange to me. The newest one from 2020 also does not have the yellowing. They are all not in direct sunlight. Wonder or it is just the effect of light and time on the white cover, the amount of exposure on each unit could be the difference in yellowing then, but it still feels quickly to me for that to happen.