Image by Image:
#1 To me, it's unfocused from a composition standpoint. cropped too tight, objects in the background and placemat distracting. Focus, Focus, Focus....
#2 Focus/focal point seems to be random, DOF seems a little shallow as well. I know you're just being give these, but the presentation is all wrong, the plate could have been dressed much more appealingly. the placemat is distracting and draws the eye away from the dish as well.
#3 lighting's a little hot, a smaller softbox, or larger with the head moved in to taper off the light, would give you a better shadow on the food. Shadows keep things from looking like they are just floating in space. Another "trick" that works well is to grad your lighting from front to back, so as you go further back in the image, it gets a little darker. It has to be done subtly, but you'll know when you get it right immediately, it makes the foremost subject almost pop. Attention to detail: loose black bits make the food very unappetizing to my eye. Chopsticks lead the eye out of the image, and are distracting
#4. Plate not dressed very well, lettuce and peppers not visually supporting the main subject, burn marks on the edges are a bit more than "browning". Overall lack of attention to the little details, note the spill to the left and top of the sauce, for example. Don't know if it's too dark, it's too cool in the highlights though... placemat distracting
Some advice for your next food job:
Be sure to note in the contract (you did execute a contract, right????):
You will be shooting for 6-7 hours, when the restaurant is not open to the public.
That you or a food stylist will dress the plates.
You will require 5-10X the product required to be in the final image to allow you to select the very best ones.
Some advice in general:
Soften up your lighting, alot...specular highlights should accent, not become the focal point.
Use manual white balance, shoot raw and focus manually. Use gaff tape on your lens if the zoom or focus creeps whatsoever, very few still camera lenses are parfocal, and focus will wander. (google parfocal zoom lens...)
Crop looser, final crops can be done in Lightroom, Aperture, GIMP or Photoshop (final cropping should be the very last thing you do)
Buy a Kodak Q13 or Q14 and learn how to use it to ensure accurate color. No need for a Macbeth or other ridiculously expensive color profiling solution if you can understand how to use the Kodak grayscale/color checker) Your white balance is all over the place, each of the plates in these 4 images should be exactly the same color, they're not even close. Every camera is non linear across all three channels, using the gray scale card will allow you to fine tune (using curves) color balance at each step from white to black, should you desire or need to.
Eliminate all ambient light, use (buy/rent/borrow) studio lighting and learn how to ensure your modeling lights don't influence your shadow white balance
Hire a food stylist, seriously. Bill it at cost +10%, it's worth it.
Never eat the food, even if they insist, charge enough to go out and buy a meal in a good restaurant afterwards with your wife/significant other.
I'm a bit of a perfectionist and hyper critical. Don't take it personally, some of my fellow students did during crits and it could get ugly, it's not personal, and an honest attempt at helping you.