Leggy rocoto chillies

Hi,
I have a selection of chillies growing on a warm, sunny, south-facing, windowsill with foil reflectors. All my annuums chineses and baccatums are nice and compact but my yellow rocotos  look leggy and a bit weedy despite the fact that they are in bigger pots than everything else. Can anyone suggest what might be the problem as there must be enough light as the other plants are all fine  .
jon

Unfortunatly the rocotos were starting to get leggy in their old pots that they were a bit pot bound in so I don't think its the pot size, but thanks for the advice. I'm just about to repot some other species and i will make sure i only use a small jump in pot size.

I've also had leggy chillis (some were locoto) and thought at the time that they were getting plenty of light. I've subsequently decided that they weren't getting nearly enough. (Having repotted, buried the suckers up to their necks, and placed out in the gh during daytime, they've really beefed up.) But I've also wondered about my growing medium. I used some stuff supposed to be great for fully fledged plants, rather than using something like Innes no2. What other factors are there - heat (constant/fluctuating), water (how much and when), variety pecularities? Phases of the moon?! I still reckon it's mostly down to light. Maybe peppers need a lot more than the other things you were sprouting?