If you haven't fed and you start showing deficiencies it's time to feed. How old the plant? What's your watering method until runoff? Do you ph water? Phing ff ocean forest or happy frog isn't needed until your soil is depleted and you have to start using liquid nutrients. Check soil ph by slurry test or runoff reading before feeding to insure your mediums ph is correct for nutrients consumption. While you have the runoff go ahead and check ppms as well just to see what's in the soil still
Whenever a issue arises checking medium is a good first move that will almost always let you know what you need to do next. If it's not medium its environment/pests