Bigger pitchers

[Plantorio]

Hi all,
I have two small N. x Hookeriana plants in an enclosure and they are growing well and producing pitchers at a fast pace. But I have noticed that the newer pitchers are smaller and very green compared to the old ones left from when I got the plant which are darker, larger, and slightly spotted. So my question is what is missing? Do they need more light hours or a stronger lamp? Should I feed the pitchers more? The feeding part will be tricky since the newer pitchers have such dang tiny openings.
All advice is appreciated
Thanks

 

[hcarlton]

Stronger light. Pitchers will not form, or remain too small, if the plant doesn't have energy to make them, and energy only comes from light.