A question about cloud cover

[hamfan]

First of all, hello again! I just got back to playing this game, and I encountered this.

I'm 155 turns into a game and I'd like to know why all my settled planets suddenly developed thick cloud cover? At first I thought it had something to do with terraforming but then I noticed my homeworld also got the same special.

Kudos for making such a great game as well.

[eleazar]

It is the result of the planetary stealth technology you researched.

[em3]

On a side note: shouldn't thick cloud cover reduce max population of phototrophic species?