Dean,
Technically these shots are very good.

Shrimp flowers:
Focus - I think you got that good. And combined with the DOF, you have the entire flower in focus and the rest out.
Lighting - Not bad. The shadow side is a little dark, well not as myuch dark as noisy. Had you moved around a little to your left you may have had more even lighting. But on the left side of the flower you have some good detail in the pedal texture that shown fairly good lighting.
Exposure – Damn good. I would have made it about 1/3-1/2 stop darker. The Dynamic range is fairly large between the whites and the shadow of the yellows and you maintained the highlight details. I would also compress the histogram a little or said differently, a little more contrast maybe.
Color – Hard to say here, I wasn’t there. From similar flowers I have seen the color looks good.

Additionally, composition, I would have turned vertical here. There is to much dead space left and right. Also the droopy lower white parts got cropped off the frame. I know they are wilted, but still should have either been totally out of the shot or all in. Also the leaf jutting into the upper left is a distraction.

White Crown of Thorn flowers:
Focus – I think it is a little soft. I assume it was the front most flower you wanted in focus, and the low contrast in that make it a little difficult to see. On the other hand, you seemed to have plenty of light and I would have stopped down to increase the DOF. These flowers are so small, you should have been able to get all 4 in focus with a f22 say. Of course that assumes your lens is ok at that aperture.
Lighting - Pretty nice, white is tough. In the front flower I can see some pedal texture and that’s good. However with the lack of DOF the flowers on the right have less detail. And the flower on the left lost it’s detail from the bright direct lighting.
Exposure – Maybe 1/3-1/2 stop over exposed. You have lost detail in the white areas, nearly blown out but not totally. Also why did you shoot at ISO800?
Color – If the white flowers are white then you got it.

Additionally, composition, I would have turned vertical here also.

Technically I think you made out pretty damn good, I would drop down on the ISO a little to reduce some of the noise, and slightly reduce the exposure. Otherwise you would see bigger improvements with compositional changes.