Nutrient Burn is one of the more common issues with new growers and stems from one of two causes. The first is from providing too strong of a nutrient mix, or by adding too high of a concentration to your plants. The second is from watering too frequently with nutrients, and not on an appropriate feeding schedule. The easiest way to spot this issue is by looking at the tips of your can leaves. The tips of the fan leaves will be yellow or brown in color and seem burnt. As this problem progresses, the sides and edges of the leaves will also change in color.
How to Cure:
This is an easy fix and requires a few steps. First, you will want to flush your plants to get out the high concentration of nutrients. This will be done by providing only plain pH'd water for the next 4 waterings. Next you're going to want to start with highly diluted nutrient mixes and slowly work your way up in strength until at full strength. To dilute, start with half the recommended doses per mix and go from there. You also want to be on a proper feeding schedule. So be sure to only add nutrients to the mix every 3rd or 4th watering. The others should be plain pH'd water. Finally, always make sure you are pH'ing your feedings properly or else you will never be able to fix these issues!