Please help out with some advice for my plants

I have 4 plants growing in hydroponic, and the very tips of the leaves are turning yellowlish brown, What can be wrong my temp is 75-80 humidity 45-50..Even the leaves that are just coming out the tips are brown..What should I do....Also on some of the leaves the blades are doing the same thing...

sounds like nute burn. flush the medium and use less nutrient. It also might be that the light is too close the plants.

Post some pics and we will get to the bottom of it.