HELP! 10 days ago I made a batch of strawberry jam. One batch didn't set up, but I waited, hoping it would. I just checked and it still hasn't set up. What can I do? Open up all the cans and re-boil? I made it with strawberrys and sugar - nothing else. Can I add pectin at this point? How much would I need? I've never used the stuff before - all the other cans set up fine without it.