hey allkillanofilla,
I'm going to guess that since the leaves are a nice green color but you have some tip burn, that you have overferted them. Do you know what the ppm is, which is something you need to watch closely when growing in hydro.

there's a way to grow where you won't experience this kind of problem. there's a way you can prevent this kind of thing from happening and you'll take all the guesswork out of growing. the method is this - don't try to do anything special. just get some Foxfarm Fruit and Flower powdered fert at your grow store and put two cups of it in a five gallon container and mix well, then put your plants in that and just water them when their thirsty. That will solve 99% percent of your feeding issues. You won't have to worry about salt build up. People make too much out of growing. It's just a plant. Don't do anything special and you'll have better grows.