I would rehome 3 of the sharks, it is not natural to keep them together like this and to be honest its a miracle they haven't killed each other yet.
In the wild RTBS will stake out a large territory for itself and vigrously fight other fish off out of its territory, particularly other RTBS (which it will fight to the death with if both RTBS refuse to retreat out of the territory).
Although your RTBS may not be killing each other right now, its not fair to keep them together, they are fish strongly controlled by their instincts and their instincts will be stressing them out a great deal since their urge/instinct to have their own large territory is so strong that they will never be happy being kept with other RTBS, when it comes down to it your tank is only big enough for one RTBS.
You will probably never be able to fully re-create a red tailed black sharks habitat, however you should still take note of basic aspects of their care, with one of the no.1 rules being that they shouldn't be kept together as it is dangerous to do this an very stressful for the fish involed.
Anyways, other than that the tank is not over-crowded at all however the clown loaches will outgrow the tank at some point in the future. If you sort the shark problem out and either make plans to get the clown loaches a larger tank in the future when they need it or rehome them at some point, the tank stocking sounds ok and would even have space for more new fish depending on what they are

.
I would advise keeping an eye on the betta though, is it a male one and what variety of betta is it (veiltail, crowntail, halfmoon etc)?
What are the genders of your platys do you know?