Betta Fish: What caused him to rip his fins?

So Sarai ripped their fins..again. the first time it happened was because of the driftwood so I took it out, but their fins ripped again. I’m thinking that maybe the leaf hammock or the heater did this (the leaf hammock is on the ground for whatever reason, keeps falling off the glass). Everything else in there is just plants and the sponge filter (as well as the thermo). I have the supplies to treat finrot if she develops it again, I also have stressguard that I will continue to use so I’m not worried about taking care of her fins, I’m just confused on how it happened.