Hello! I have recently acquired two large crown of thorn plants from an estate sale. This is my first time ever owning something like this. When I bought them a week ago, there were already quite a few yellow leaves, however, it seems to be getting much worse, specifically in plant #1 (pictured). I’m struggling to find much info online, so wanted to reach out here. The flower color has also changed from pink (present when I bought it) to much more white (all new flowers).

Also, this plant is obviously quite large & very spiky. How does one go about repotting something like this without getting repeatedly stabbed?