  We present the results of spectroscopic and photometric observations for
three hot southern-hemisphere post-AGB objects, Hen 3-1347 = IRAS 17074-1845,
Hen 3-1428 = IRAS17311-4924, and LSS 4634 = IRAS 18023-3409. In the
spectrograms taken with the 1.9-m telescope of the South African Astronomical
Observatory (SAAO) in 2012, we have measured the equivalent widths of the most
prominent spectral lines. Comparison of the new data with those published
previously points to a change in the spectra of Hen 3-1428 and LSS 4634 in the
last 20 years. Based on ASAS data, we have detected rapid photometric
variability in all three stars with an amplitude up to 0.3 mag, 0.4 mag in the
$V$ band. A similarity between the patterns of variability for the sample stars
and other hot protoplanetary nebulae is pointed out. We present the results of
$UBV$ observations for Hen 3-1347, according to which the star undergoes rapid
irregular brightness variations with maximum amplitudes $\Delta V$=0.25 mag,
$\Delta B$=0.25 mag, and $\Delta U$=0.30 mag and shows color-magnitude
correlations. Based on archival data, we have traced the photometric history of
the stars over more than 100 years. Hen 3-1347 and LSS 4634 have exhibited a
significant fading on a long time scale. The revealed brightness and spectrum
variations in the stars, along with evidence for their enhanced mass, may be
indicative of their rapid post-AGB evolution.
