  The MIR blend fluxes correlation between HCN and water can be explained as a
consequence of dust evolution, namely, changes in the dust MIR opacity. Other
disk properties, such as the disk inner radius and the disk flaring angle, can
only partially cover the dynamic range of the HCN and water blend observations.
At the same time, the dynamic range of the MIR SED slopes is better reproduced
by the disk structure (e.g. inner radius, flaring) than by the dust evolution.
Our model series do not reproduce the observed trend between continuum flux at
850 {\mu}m and the MIR HCN/H2O blend ratio. However, our models show that this
continuum flux is not a unique indicator of disk mass and it should therefore
be used jointly with complementary observational data for optimal results. The
presence of an anti-correlation between MIR H2O blend fluxes and the MIR SED is
consistent with a scenario where dust evolves in disks, producing lower opacity
and stronger features in the Spitzer spectral regime, while the gas eventually
becomes depleted at a later stage, leaving behind an inner cavity in the disk.
