What you can do is return all those fish you added to the tank.
Male blue (three-spot color morph - all your gouramies are Trichogaster trichopterus except the 'moonshine' which is probably Trichogaster microlepis) are particularly aggressive and territorial fish and, to be kept with other gouramies, need a lot of room and a big group of females. Keeping two male together almost inevitably results in the death of one or both of them as they tend to fight with each other - often as brutaly as Betta splendens - and, if they don't out-right kill each other, the stress and injuries usualy leed to death.
Adding the other gouramies when your original fish had already settled into its tank and established a territory only made things worse as it would have viewed the newcomers as 'intruders' and would have wanted to get rid of them. If this had been a larger tank and you added a large group of female gouramies, things may well have turned out ok as any aggression displayed by the male (assuming it was a male) would have been split between the females , diluting it and making it less severe.
Note that, whereas you can keep a male with a group of 2 or more females, the tank needs to be heavily planted/have lots of hiding places and it needs to be quite large (30 gallons would be the absolute minnimum for a trio but more is better). You also need to consider that three-spots are the easiest gourami to spawn - but when they spawn, all hell breaks loose as the male becomes especialy aggressive as he guards his nest and, at this point, he may turn his attention towards non-gourami tankmates as well as his mates and it's not unusual for male three-spots guarding their nests to kill fish they'd otherwise ignore (such as rasboras or cory catfish). Basicaly, if you want a mixed-sex group, you need to be prepaired in case they breed. Heavily planting a large tank and keeping the water flow relatively strong and the temperature relatively low will help reduce aggression/chances of them breeding. But, if they breed, you need to only have very fast fish (such as danios and some barbs - but nothing nippy as that'll just provoke the gouramies even more) or fish that'll stay well out of the way (eg: nocturnal/semi-nocturnal catfish, most plecs, some loaches etc).
Because your tank's not big enough for mroe than one three-spot (and therefore not big enough for any other gouramies), you need to re-home all of your except one ASAP.
Also, moonshine gouramies (assuming we are talking about Trichogaster microlepis) grow to at least 7" and, while they are less aggressive than three-spots, need to be in a bigger tank.
