Leaves, rust dots, yellowing margins

Did those leaves come off the top or bottom of the plant?

Yep best advice is below definitely 👌

Down below.

Looks like a calcium deficiency. Coco always needs extra cal mag. The other option is your ph in your coco is getting out of range. In heavy flowering in coco for myself my ph will rise causing lock out if I don't heavily dose it with extra potassium and phosphorus to maintain and stabilize it. Lack of enough nutrients is what does it to me. I would run a ph 5.8 water through till run off. Get a test reading of ph. If it is 6.3 or up there is the problem. Ph is very important in coco grows, but results are strong. Feel free to dm me if you need more assistance. Happy growing 🌱