  We explore the growth of the stellar disks in 14 nearby spiral galaxies as
part of the Deciphering the Interplay between the Interstellar medium, Stars,
and the Circumgalactic medium (DIISC) survey. We study the radial distribution
of specific star formation rates (sSFR) and investigate the ratio of the
difference in the outer and inner sSFR ($\Delta_{sSFR}~={\rm sSFR}_{out}-{\rm
sSFR}_{in}$) of the disk and the total sSFR, $\Delta_{sSFR}$/sSFR to quantify
disk growth. We find $\Delta_{sSFR}$/sSFR and the HI gas fraction to show a
mild correlation of Spearman's $\rho=0.30$, indicating that star formation and
disk growth are likely to proceed outward in galactic disks with high HI gas
fractions. The HI gas fractions and $\Delta_{sSFR}$/sSFR of the galaxies also
increase with the distance to the nearest L$_\star$ neighbor, suggesting that
galaxies are likely to sustain their ISM cold gas and exhibit inside-out growth
in isolated environments. However, the HI content in their circumgalactic
medium, probed by the Ly$\alpha$ equivalent width (W$_{Ly\alpha}$) excess, is
observed to be suppressed in isolated environments, apparent from the strong
anti-correlation between the W$_{Ly\alpha}$ excess and the distance to the
5$^{\rm th}$ nearest L$_\star$ neighbor (Spearman's $\rho=-0.62$). As expected,
W$_{Ly\alpha}$ is also found to be suppressed in cluster galaxies. We find no
relation between the W$_{Ly\alpha}$ excess of the detected CGM absorber and
$\Delta_{sSFR}$/sSFR implying that the enhancement and suppression of the
circumgalactic HI gas does not affect the direction in which star formation
proceeds in a galactic disk or vice-versa.
