how often are you watering?, how far are they from the light source, are you over fertilizing?, can you take pictures from further away, of the whole plant?
Just at the max nute uptake. Soldier on. Add less Nitrogen.
Most likely what @Storm said. Skip a feeding and do water only. Keep an eye on it.
A full plant pic would be awsome.
Have you ever feed your plant @UncleDick if so how much the white on tips is normal my friend
how often do you water?, how often do you fertilize?, whats your soil composition?