  Stars are likely to form or to be captured in AGN disks. Their mass reaches
an equilibrium when their rate of accretion is balanced by that of wind. If the
exchanged gas is well mixed with the stellar core, this metabolic process would
indefinitely sustain an "immortal" state on the main sequence (MS) and pollute
the disk with He byproducts. This theoretical extrapolation is inconsistent
with the super-solar {\alpha} element and Fe abundances inferred from the broad
emission lines in active AGNs with modest He concentration. We show this
paradox can be resolved with a highly-efficient retention of the He ashes or
the suppression of chemical blending. The latter mechanism is robust in the
geometrically-thin, dense, sub-pc regions of the disk where the embedded-stars'
mass is limited by the gap-formation condition. These stars contain a radiative
zone between their mass-exchange stellar surface and the nuclear-burning core.
Insulation of the core lead to the gradual decrease of its H fuel and the
stars' equilibrium masses. These stars transition to their post-main-sequence
(PostMS) tracks on a chemical evolution time scale of a few Myr. Subsequently,
the triple-{\alpha} and {\alpha}-chain reactions generate {\alpha} and Fe
byproducts which are released into their natal disks. These PostMS stars also
undergo core collapse, set off type II supernova, and leave behind a few
solar-mass residual black holes or neutron stars
