Measuring Small and Kidneys

We had a scan last week, 32+6 days and out little guy is measuring small. He was measuring big early in pregnancy but now we are all the way down to 17th percentile. How worried should we be? Anyone else measuring small? My belly is measuring about 2 weeks behind too. I went and stocked up on calcium rich snacks and ensuring my protein intake is where it needs to be. We were also told he has a minor kidney issue. Something about may create a blockage or something later. We don’t fully understand this but they keep measuring and say the issue isn’t worse or better just needs to monitored. So worried about our baby. Anyone else out there with experience on this?