I am afraid you have some very serious issues with this combination of fish, in a 20 gallon tank. It is likely part of the ammonia problem too. I will just mention the issues, but please work towards resolving them. The fish are not going to bee healthy unless things change.
The Tiger Barbs must go, as they need at least 8 and this requires a 30 gallon tank just for them. They are notorious fin nippers, and in this small a group they will be stressed and get very aggressive as their frustration rises.
A betta is not compatible with any of the other fish. He will be stressed, and likely feel threatened too.
The gourami might be OK but not with the Betta, barbs or cichlids.
Neither cichlid will work together, or in this tank, or with the other fish.
And before you say it, if the fish "appear" to be getting along, that is deceptive. The above is causing them stress, guaranteed, and this will heighten until something snaps. I am sure you want them to be happy and healthy, so changes must be made very soon. If other tanks are not possible, the store may take them when they know the problems.