The reason they change the names on fishes is that they often just call a fish by a name of something similar when first discovered, eg;pseudotropheus...currently there are about 200 species a year being discovered, its up to the scientists to argue over later, when they get to examine a fish they notice differences, eg; scales, teeth...from there they get re-classified.
Another thing is in the older days there weren't as many species, Alot of Tangy's were Neoloamprologus, Malawis were Haplochromis.....
as for the fish in the pics,
1) I think Aaln is right. Hard to tell with rainbows
2) Astatotilapia brownae, formely known as Haplochromis
3) Copadichromis azureus, the sciaenochromis are more slender
4) Metriaclima callainos, cobalt blue
5) Maylandia Estherae, red zebra
6) Maylandia Crabro, bumlebee cichlid
Hope this helps.
Frenchy