They all make an emphasis on your GFR is you are under 60. I’ve been maintaining 43-57 for 15years and only went lower when I had a bacterial infection and once that was under control it climbed back up. You may have some things like hydration or type of food issues going on. Increase water intake, as suggested cranberries or cranberry Juice, avoid high fat dairy, avoid alcohol, reduce or consider eliminating red meat, avoid purines ( liver, heart, etc), etc etc see healthy kidney diet. I would try some of these and request to see what your GFR numbers are like in a couple months. If there is still concern or it’s going lower I’d ask to see or speak to a nephrologist that specializes in Kidneys and CKD.