I just bought a canning set (for water bath) and made jam (my first time) last night. It's blackberry jam. I ended up with 7 8oz jars. Well, 4 of the jars when I tilt them over it doesn't run so I'm assuming it set right. 3 of the jars, when you tilt them it runs, so it didn't set right. How can I fix these 3 jars? Why did 4 of the jars set but 3 not?