I asked in a discord what to do andthey just said: "Buy Aerosoft LSZH", which I don't want to do.
The best way to get wrong info, is to "ask around on forums". Always as to the source...As you noticed, the problem happens only at other sceneries like UK2000, so it should have been obvious it wasn't a problem of the scenery, and it will happen with every scenery.
Those spots are the result of combination of the DXT compression that *every* scenery use (if it used 32 bit uncompressed textures the fps will go to the floor, since they would exhaust the video memory very quickly), and the fact the sim has a more limited dynamic range at night.
Normally, you don't see them much, but since you are using PTA, it's likely that some "enhancement" set by that product, has altered the night rendering, making them more visible. Here's a similar thread about KCLT having bright colored spots on grass, which of course was caused by PTA:
http://www.fsdreamteam.com/forum/index.php/topic,16526.msg117805.html#msg117805
