Observed (black dots) and synthetic spectra around the Ag I line at λ=3382.889 Å for the four target stars. The synthetic spectra were computed for A(Ag)=−∞ (gray line) and for the final abundance value from Table 2 (red line). The red shaded area corresponds to abundance variations in the amount of the standard deviation. In the case of 2M18453994, several syntheses from A(Ag)=−1.5 dex to 0.0 dex in steps of 0.25 dex are shown to illustrate the choice of the upper limit.