I have been a jam maker for years. We live in an area of fresh fruit so it's always naturally sweet. I decrease the sugar in each recipe by at least 1 cup and I always add fresh lemon juice. My question is: do I need to water bath the jam to prevent it from turning dark on the top?

It doesn't affect the taste but it doesn't look very pretty. I have jams I recently made & I'm also wondering if I could water bath them now even though I made it a few weeks ago? I pack hot jam into scalding hot jars with hot lids. I always have good seals & I love the sounds of the jars sealing! I call it the Canner Symphony!