My lab numbers have fluctuated month to month some too. One time when the protein went up quite a bit unexpectedly, my nephrologist put me on an ARB (angiotensin receptor blocker). It seemed to help a lot with the protein and with my suddenly very high cholesterol too. I am off it now, and thankfully don't have measurable protein in my urine.
Each person is so unique. What worked for me might not be best for you. I hope your numbers improve. I had a few months in a row where everything seemed to be going the wrong way, and then things got better without any reason that i could tell. My doctors were more calm about it all than I was. It's important to talk to them when we have concerns, I think.
Have your overall lupus symptoms gotten better over time? Mine can still be fairly disabling.