Actually i wouldn't say its overstocked considering is a 15 UK gal, and not US. Certainly not "Waaaaayyyyy overstocked" as riverman put it

. Its just the combo of fish and critters that could need a little working on, the only thing in there that will outgrow the tank is the armoured shrimp. Your current stocking;
5 Neon tetras
2 Amano shrimp
2 Bronze cory
2 Kulhi loaches
1 Guppy (Male)
1 Dwarf gourami (Female)
1 Betta
1 Bamboo shrimp
1 Cameroon/cameroun armoured fan shrimp
1 Bristlenose plec (Female
For more info on critters like shrimp, check out;
http
/www.shrimpcrabsandcrayfish.co.uk/Sh...p.htm~mainFrame
Rehome the betta and the guppy- male bettas are not suitable for community tanks, and guppys are sociable fish that need to be kept in groups of the right gender mix. Tetras do best in groups of at least 6, so i would increase the neon tetras (these fish are not suited for new tank set ups though, so if yours is new i would advise you swap them for somthing more hardy and suitable, as neons can be very fragile fish).
Khuli loaches would do better with another one or two of them, as they are sociable fish- so do cories and amano shrimp.
Personally, i would chose between the cories and the khuli loaches, as they essentially do the same thing in the tank and take up the same space. I would have either corie or khuli loaches in the tank in decent numbers, but not both.
It would be better if your stocking looked more like this;
6 neon tetra
1 dwarf gourami
4 bronze cories or 4 khuli loaches
3 amano shrimp
1 bamboo shrimp
1 Bristlenose plec.
This is the most i would advise for your tank, depending on how mature it is and the tanks dimensions.
Rehome the armoured shrimp, betta and guppy. Rehoming the bamboo shrimp is advisable if your tank is under 6months mature, as due to being filter feeding shrimp they rely on a steady flow of mirco organisms and microscopic bits of food in the tank water, but can slowly starve in tanks not mature enough.
How long, wide and high is the tank and how long has it been set up? What sort of filtration do you have in there

?