Why irregular pitchers?

[tzestan]

I have a plant for nearly 5 months.

When I just bought it, it came with relatively big pitchers.


But since then, pitchers have been growing irregular in size and colour.
Generally smaller than when I first acquired it. Including abnormal pitchers.



Plant seems to be doing fine, but the newest shoot looks growing on a much elongated stem.

Any comment on what could be the cause of small and irregular pitchers?