Why are my leaf tips turning white
This is a fairly common question. More often than not the problem is a very minor nutrient burn. Typically growers experience this problem in the first few weeks of the vegetative stage, when growers are beginning to introduce more nitrogen to their plants.
As you can see in this image the nutrient burn is very mild with only the tips of the leaves showing any signs of burn. If you look closely you can see that the very ends of the tips are not only a lighter color but the very ends of the leaves show signs of what looks like actual burn.
The best way to correct this issue is to simply reduce the amount of nutrients you are providing the plant, until the plant has grown larger and can utilize all of the nutrients that you are providing it. Many growers will allow their plants to show small signs of burn with the belief that they are providing as much nutrients as possible, I have found this to be a determent to the plant and would argue that reducing the nutrients provided is the best bet.