As Brad said it is bacterial bloom probably due to uneaten or other matter decaying.
Do a water change and if you have a gravel cleaner use it to take out any excess food and other stuff that could be the cause.
Also as mentioned if you change all or too much of your filter media at once the bacteria are not there to convert the rotting stuff through the cycle so other bacteria begin to eat it. O wise ones correct me if i'm wrong :oops:
It will clear up once the cause is fixed.
As for the Kissing Gourami you might have to move him. How big is the KG compared to the other fish. From what ive heard they're better kept with fish their own size or larger - Please correct me if i'm wrong again :oops:
Hope it helps
Kiran :bounce: