Leaves curling down with brown tips sounds like it could be nutrient burn (too much nutrients). Does it look sort of like this?
If so, you should try feeding your plant just pH-balanced water (without nutrients) for a few days, then slowly re-introduce your nutrients. When I'm flushing, I like to dissolve sugar into the pH'ed water to help leach out any nutrient salts. If you look on the ingredient in Clearex, which is a commercial salt-leaching solutions for gardening, you'll see that the only ingredients are glucose and sucrose (sugar).
If you just recently transplanted, there may have been nutrient 'hot spots' in the new soil which caused your plants to get nute-burn.
If you're just getting spotting around the edges, like this:
Or if you're getting spots on the leaves like this:
Then you have some sort of nutrition deficiency in addition to any nutrient burn you may have. Your best bet in that case would be to flush the system thoroughly with pH'ed water and then feed your plants with about a 1/2 dose of regular nutrients. Sometimes you get deficiencies because the pH is off, or because there's too much of another nutrient in your growing medium which is preventing proper absorption. However, if you flush and then re-feed with nutrients, you would take care of either problem.