Top: continuum-subtracted JWST/MIRI spectra of 3I in the ν₂ band of H₂O from both epochs, with the best-fit PSG coma fluorescence models overlaid. For the H₂O and CO₂ analyses, spectra were extracted using a 2″–3″ annular aperture, to avoid optically thick regions, while for CH₄, a circular 3″ diameter aperture was applied. The plotted error bars are based on the measured uncertainties from the spectral extractions and have been scaled to yield a reduced χ² of unity for the best-fit models. The contributions from ortho- and para-H₂O are shown separately in blue and green, respectively. The line intensities are significantly lower in the second epoch, corresponding to a sizable decrease in H₂O production. Bottom left: analogous fits to the ν₂ band of CO₂. Bottom right: CH₄ fluorescence model and data. The emission feature highlighted in purple at 7.5066 μm is from the ground-state forbidden transition of Ni I. To illustrate the systematic decrease in production between the two epochs, the vertical scale is identical within each set of panels.