Sorry, my mistake. They should be listed only once.
Note that in your original equation
2 = ( [Mn^2+] -( [Mn(NH3)] + [Mn(NH3)2] + [Mn(NH3)3] + [Mn(NH3)4] )) + [Mn(OH)2] + [Mn(NH3)] + [Mn(NH3)2] + [Mn(NH3)3] + [Mn(NH3)4]
complexes concentrations cancel out, leaving just
2 = [Mn^2+] + [Mn(OH)2]
Equation as I wrote it was wrong, but was "relatively" correct - that is, it was correct in logical terms, just the coefficient had incorrect value - so it was working better than equation that was in no way related to the situation in the solution.