The Dwarf Gouramis and the fighter are instantly ringging alarm bells, as with the word pleco..... reasons below;
3 dwarf gouramis
Males are very agressive IME, and tend to bully females, often killing them and other males. If you want to keep more than one, then only one male to every 75g (assuming lots of cover) and ensure you have 2 females to every male so that attentions are divided and the females get a break. Most males won't tolerate other Ambanitard type fish (their family, and also the one that fighters fall into) and some males (depending on personality) develop into fin nippers. They grow to about 4 inches each
12 inches of stocking used
1 angelfish
Grow tall and need a relatively tall tank. If your tank is under 18inches tall, you will need to re-home this fish later as it will get too large. Should grow to 8 inches long and a foot tall in the common veriaty Veil tails can have 2ft of fins on them... Nice fish, but one for larger tanks usualy. Can eat small fish, and can also be nippy. Suseptable to fin nipping.
8 inches of stocking used
1 male siamese fighting fish
Some males (but not all) can be agressive to other fish, and they are very prone to fin nipping. Idealy they should be kept alone, or have the rest of the tank's decoration, filtration and stocking planned arround them. Grow to about 4 inches
4 inches of stocking used
pleco
What type. These grow between 4 inches and 6ft depending on species. This fish could be a briliant fish in the tank, or simply too big. These fish vary a lot in behavior, decoration and dietry requirements. Google common plecos, gibesepse plecos and bristle nose plecos to see if it is anything like these.
Stocking we usualy recomend a new tank and or fish keeper stick to one inch of adult fish length per gallon of water. A 84l tank is roughly 22US gallons. This gives you 22 inches of fish to play with. A new tank is one that is under 6 months old.

You currently have 24 inches of fish in use ATM
excluding the pleco, as I don't know what type you have. IMO for the time being the tank is stocked. Once the tank gets to 6 months old, you could mebe think about adding more fish, but for the moment, I wouldn't add any more fish.

A tank can take 2 inches of fish per gallon assuming it is mature and has good filtration
HTH some
Rabbut