N or K def..? what to do?

Hi every1 am working on my first grow which is on soil but I have a problem the plants are on veg and the leaf's tips are getting yellow. I did some research and the reason for the problem cuold be N or K def.. My question is how can I fix this? remember this is my first time, my plant is to flush them but I don't know what to do afterwards. any help is apreciated.

peace

No Pics, no definite answer.

Heat stress, lack of Light, over fertilizing, burning, ect...

ok, I don't have any camera at the moment, can anybody tell me how is the flushing process or if there is any other way to deal with it.

Water your plant enough to fill the pot 3 times over with just H2O. Slowly. This flushes out all the nutes in your soil in the case of over fertilizing. You do it if you have nute burn. Or if you put something stupid in your soil. I read that one guy fed his plant a cup of coffee. That was funny. He had to flush. Be careful doing it. It causes stress on the plant. Needs to be worth the stress.