fish mix is really strong, plants cant have N deficiency on it. your ph might be off, it looks ph to me. too early to have nutrient burn so it most likely can not be able to absorb elements due to off ph. check your soil ph my advice. drop your watering ph to 6.3-6.4 for a while and check again. giving too much nutrients can also drop soil ph. 4ml is too much for fish mix. really it is strong, 2ml MAX in my opinion.