i take it your using vray plane lights, try turning off affect reflections, as it always tend to reflect a square which you can pick out.
With regards to the diamond, if your lights weren’t so burnt out you’ll start to get more detail in there.
May want to render a few pass’s off, one with the lights just affecting diffuse, then add on specular afterwards and it photoshop blend between the 2 to get the desired result.
I always try to think in terms of rehality rather than 3D, so in a studio setup surely one would see the reflection of the strobe units in the metal. If I where to turn off affect reflection for the lights, will the metal not look very flat as there would be nothing for it to reflect?
Which blending mode would you recomment in PS and which of the two passes should be on top?