Lyric problems

[Seng Liang]

Hi, I'm using Lilypond 2.7.12 for Windows 98 and I am having some lyric 
difficulties. Here is the file:

\version "2.7.12"

\relative c' {
\set Staff.instrument="Soprano"
        \clef treble  #(set-accidental-style 'modern) 
        \key f \major 
        \time 2/4
     \autoBeamOff  \override Score.RehearsalMark #'padding = #2.5 
 f'2 g, c a' f << { \tiny g c f,4 } \\ { \normalsize g,2 c f,4 } >> r4  
\bar ".|."      }
  
 \addlyrics { Al -- le -- lu -- ja,  al -- le -- lu -- ja. }

I would like to know why are the lyrics in bar 6 to 8 missing? 
For these bars, there are no changes in melisma and note durations, the only 
difference is the pitch between these two voices.
Therefore, how can I make the words "le", "lu" and "ja" appear only once 
respectively on the notes g2 c2 and f4?
Thank you.