I've noticed that N. ventricosa can take awhile to produce new
pitchers after it has been stressed. Give it a couple of months.
What are the temps like in the area where you are growing these?
Is it staying really warm at night? You'll want these plants to
be cool at night. They might also benefit from a bit more than two
hours of sun per day, although you don't want to burn them.
Finally, the plants may not pitcher well if your humidity is too low.
I used to live in Santa Barbara, and as I recall, the humidity there
is not generally very high.
Jeff Shafer