Thanks to you guys, I just discovered that I've been feeding Oxalis stricta to my sulcatas for years. I thought it was "clover" and totally fine. The site that I looked at said its good for flavor in salads, but not in large quantities due to the high oxalic acid content. They've only had a few handfuls over the years, with days or weeks in between, and it doesn't seem to have bothered them. They live outside in the sunshine, get CA supplementation occasionally, and have a very varied diet, so I think we'll be okay.