I don't know why...

I was playing SimCity normally when I reached level 8 and unlocked new buildings, like the sewage system. I placed the appropriate buildings for those functions, but my Sims' happiness was dropping even though all the functions were colored blue in the "government" section. I really don't know what to do! Can you help me? Because it's bad to drop from 97 to 65 happiness for no reason.  

Greetings from a big fan of yours who keeps all your games, Sunny