Kratom foamy urine/flank pain

So I used feel free/kratom capsules for about 1 year. I started having mild flank pain fairly quickly while using kratom. I pushed through that thinking it was nothing and ended up using it for almost exactly 12 months. The reason I ended up quitting (21 days off) was due to foamy urine that popped up about 1 month ago. I’ve had 2x urinalysis and blood work done and my gfr is over 100 and I have no detectable protein in my urine. Has anyone else had this flank pain/foamy urine combo? Does it go away? What is the cause of the foam if it’s not protein. Before people start saying thing like fast stream and toilet cleaners.. it definitely is not that. Thank you for the help! Really curious what’s going on with me.