Panels (a1) and (a2): W_C,N,O,Na vs. log(M/M_⊙) and [Fe/H], respectively. Panels (b1) and (b2): same as panels (a1) and (a2) but for W_Mg,Al. GCs within the 5.5 < log(M/M_⊙) < 5.9 mass interval used to remove the metallicity dependence (see text for details) are encircled in yellow. Panel (b3): resulting width after removing [Fe/H] dependence (ΔW_Mg,Al) vs. mass. Panels (c1) and (c2): total width of light elements involved in the multiple population phenomenon W_{C,N,O,Na,Mg,Al} vs. mass and maximum helium spread measured by Milone et al. (2018), respectively. The Spearman correlation coefficient and its p-value are reported in each plot as in Figure 7.