Questions on top dressing

Has anyone ever used Gypsum? Made the mistake of using shit soil and using bottled nutrients for feeding. They're not doing bad just looks like they need some sulfur. I purchased the Down to Earth gypsum and I'm not finding too much Info on how much to use for a top dressing. Or is there a better source for adding sulfur?

What's makes you think they need sulfur? Pics could help.

The new growth is a lighter green than the rest of the plant. It may be completely fine, but I'm using foxfarms grow and micro for feeding and sulfur is not in the nutrients. Just added lime today for a top dressing because my soil ph was around 4 according to the meter. Idk how they've made it this far in that.