You can really see the deficiency issue. Is that a defoliated plant? I've been doing a bit of research on this one because if you for example look at shwazzing the guy who promotes it recommends very high nutrient strengths and I expect he discovered this through trial and error. I.e. when he defoliated he saw deficiencies. Answer feed more. From a scientific perspective the literature supports this... E.g.
studies have shown numerous grazing-tolerant C3 and C4 forage grasses growing with high nutrient availability in controlled-environment or greenhouse conditions have demonstrated that root elongation essentially ceases within 24 hours after removal of approximately 50% or more of the shoot system and root mortality and decomposition may begin within 36-48 hours. Root respiration and nutrient acquisition are also reduced following defoliation, but to a lesser extent than root growth. Root respiration begins to decline within hours of defoliation and it may decrease substantially within 24 hours. Concomitant with the reduction in root respiration following defoliation is a rapid reduction in nutrient absorption. Experiments conducted with perennial ryegrass growing in nutrient solution demonstrated that the rate of nitrate (NO3-) absorption began to decline within 30 minutes following removal of 70% of shoot biomass. NO3- absorption decreased to less than 40% of the pre-defoliation rate within 2 hours following defoliation (Clement et al. 1978). In these experiments, NO3- absorption continued to decline over the next 4-12 hours until it became negligible for 2 or 7 days before recovery began under high and low light intensities, respectively. NO3- absorption did not resume until a positive daily carbon balance was reestablished within the plant (Clement et al. 1978). Rapid reductions in root respiration and nutrient absorption following plant defoliation are proportional to the intensity of defoliation (Davidson and Milthorpe 1966a, Thorgeirsson 1988). Similarly, canopy shading or root severing causes large, rapid decreases in root respiration and nutrient absorption (Clarkson et al. 1974, Hansen and Jensen 1977, Massimino et al. 1981, Saglio and Pradet 1980, Aslam and Huffaker 1982, Thorgeirsson 1988, Bloom and Caldwell 1988, Macduff and Jackson 1992). These experiments clearly demonstrate the importance of current photosynthesis for the maintenance of root growth and function in rapidly growing plants.