Mimi, that block is beautiful and the yellow is so perfect. I hope you can save all of them.
Maybe you could undo and then replace the scorched parts?
I read that coffee has less tannic acid than tea and that your fabric would then have a life expectancy of about 75 years. I wonder how long you can expect tea dyed fabric to last. Coffee dye creates a different look than tea though and I can't see it looking nice with that cheery yellow. It has been my experience that the colored fabrics don't take tea dyeing well, but the white and cream fabrics do.