Hi @Atilio5E19 ,
With the exception of img_6175, the exposure of your files are good. Img 6175 is over exposed. All your files are lacking contrast. The first four has excessive noise. They are all not very sharp, however you might be able to get img_5836 and 5669 pass after correcting the contrast and noise. Img_5669 has color fringing at the base of the cup. That too you need to correct.
You can learn more about how to get your files accepted at this link. Also this link will give details about what you need to do to produce better quality files.
I can confirm that these photos have technical issues. I'll cover them briefly below. In general, shooting at the lowest ISO available is recommended but simply shooting at a low ISO doesn't guarantee a noise-free photo. I found the noise minimal in these photos, but I think sharp focus, lighting, and plate edges slightly out of frame were the main issues in the photos.
5669: The cups were in sharp focus, but the strawberries at the back were out of the range of focus. It appeared there was a slightly green/yellow colorcast as well.
5827: Not much in sharp focus, including the chopsticks which I consider part of the main subject. I think the lighting could have been improved, and it would benefit from some contrast or exposure adjustments.
5836: Mostly the same as 5827. Not a lot in focus, and the edges of some of the plates were clipped off. With the main plate, this appears to be a mistake even if it was intentional.
6173: The edges of the cutting board aren't straight, there is a green/yellow colorcast, and the details were a bit soft.
6176: Colorcast, the plate edge is clipped off at the top, details are soft at 100% view. It's also slightly underexposed.
In general I would up the power of the lighting by a stop or two, and make sure everything is included fully in the frame, and confirm the photos are in sharp focus by viewing at 100% view. Depth of field is tricky with a macro lens, as it gets more shallow as you zoom in closer.
I hope you have better luck with future submissions!
I should as a first say that the PPI (DPI) value has absolutely no influence non any quality attribute at all. It's only and really only an indicator for the size in inches/cm of an image at a specific pixel count. You can set it to 100,000, and it would not result in a better or sharper image. Incidentally: for a pixel picture, this should be called PPI, as DPI is a value important for print.
5696: The focus is on the wrong part of the picture, the exposure is missing the blacks:
(the focus issue can't be corrected)
5836: The exposure is missing whites and blacks.
The focus is also here wrong, you should focus on the sushi.
5827: Best picture until now. Blacks and highlights are missing.
Focus is more or less OK.
6176: Bad framing, why didn't you include the whole plate.
Same exposure problem then alls: blacks are missing. Whites are also absent.
The picture is out of focus.
6173: Exposure issues!
You need to check, especially your focus, directly on stage when taking the picture. That is really not to correct afterwards. For all the rest, you could edit and resubmit.
Photo 61723 is not focused well and the highlights on the lime are overexposed.