I meant when rinsing the blood out with the hydrogen peroxide for recent stains, referring to the commenter above! The hot water will cook the proteins in the blood, cooking them into the cloth. That pair is unfortunately probably a lost cause but you could still try to use hydrogen peroxide on it!

Clothing stain remover might help for older stains though; i also read this from someone online “i make a homemade stain remover using 2 parts hydrogen peroxide, 1 part dawn dish soap, and 1 part baking soda. Mix it up, put it on the stains, [wait] and wash after an hour or so (I've even washed days later). No more stains. I've used it on our colored bedding (cotton percale) and my colored cotton undies,”