Even if none of them are fully grown your tank is already probabaly overstocked (though only slightly atm), what are your nitrates getting to imbetween water changes? And how often are you doing changes?
Long term it's extremely overstocked and some of the fish literally just can't live in something that small. Have you looked up the fully grown sizes of your fish yet?
Incase you haven't (in brackets are rough guide to tank size for a single fish) and in
Green are my comments:
Tiger barbs - 8cm (80-100l)
The lower limit of 80l for these fish is only ok if it's a long tank 30"+ and in such a large group a much larger tank would be required for them to continue to co-exist peacfully with their tank mates once they're fully grown. I would suggest 125l min
Blue Gouramis - 15cm (200l)
I'm guessing you mean the blue variety of the gold/three spot gourami? And not the powder blue dwarf gourami? Eitherways it's way too small for even a single blue and is only just big enough for a single dwarf. You will find agression issues between the two and possibly even towards tank mates if they stay in there
Kribensis - 10cm (80l)
For them to co-exist with other fish you really need a bigger tank, if you have a male and female you'll have massive agression problems when they decide to spawn (which they will). If you have too males then in such cramped conditions they will fight amongst themselves aswell as with other fish.
Red Tailed Black Shark - 12cm (200l very min)
These fish are NASTY when the get older. If not given a large enough territory then they WILL attack tank mates. I reckon you'd find that it'll regularly fight with the kribs but will also go for other fish, the gouramis seem like an obvious target.
Pleco - Does it look like either of the following:
This is an L001 also known as a gold spot pleco. 30cm (200l very min)
Definitely need an upgrade for this fish it grows quite big and the bottom of you tank is very crowded atm.
This is an L18 Gold nugget pleco. 30-35cmcm (200l very min)
As above
Clown loach - 30cm (400l for a proper group)
These are MASSIVE fish once fully grown. They are slow growers compared to everything else in the tank but I still wouldn't keep them in that tank even as babies cause I'd be too worried it'd cause stunting issues. I'd suggest a min of 100l temp tank but tbh would probably just put them straight into something suitable
Other loach (really depends what it is) - Dwarf chain loach? Chinese algae eater? Polkadot loach? Zebra loach?
In your current situation (if an upgrade is a possibility) then I'd suggest you upgrade to a 200l long tank (as opposed to tall because you need a long rectangular footprint for your bottom dwellers).
If you upgrade in the near future (next few months) then I see nothing wrong with keeping:
x7 Tiger barbs
x1 Blue Gourami
And then picking only 2/3 species of the following
x2 Kribensis
x1 Red Tailed Black Shark
x1 Pleco
x1 Other loach
The clowns I'm afraid I have to suggest you re-home for definite unless you can upgrade them to something definitely suitable in the future(400l+) and give up all your other bottom dweller bar 1.
So say if you wanted the clowns (which need a bigger group as you said), then only keep 1 species of the following:
x2 Kribensis
x1 Red Tailed Black Shark
x1 Pleco
x1 Other loach
Hope this helps, and welcome/welcome back to TFF