Yes, if it is very humid that can cause stretching. Also if there isn't much breeze where your plant is situated this will not help matters - it won't help it to develop a thick, strong stem, and also the plant may not be getting enough CO2 as the air around the leaves tends to become "stagnant" as the plant uses up the CO2 in the immediate vicinity with no more CO2 coming in to replace it.
If I were you I'd try to make sure that during the day the plant is situated where there is a breeze if at all possible. Also bring it in at night and put a moving fan on it so it simulates an outdoor breeze. This will help to thicken up the stem. Finally I'd try to get my hands on a few CFL bulbs, the daylight (cool) ones, high wattage, and put them as close to the plant as possible (usually a couple of inches) without burning the leaves. They don't get very hot, just use your fingers to test the temperature at the leaves. Do this for a week or so and see if there is an improvement.
[I'm a great one for allowing plants to have a period of darkness as they need to respire sometimes in order to break down food etc just as we do, so I wouldn't recommend the 24 hrs of light for TOO long, but that's just me. I'd worry more about getting that stem thickened up at the moment.]
As regards, feeding, let me know more about your soil if possible. From the pics I don't see very many white balls in the soil, and they look very small, so it could very well be slow release fertilizer in which case I wouldn't add any more food just yet. Remove the food stick just in case, and try the light and fan treatment for a week and see how it goes. Just keep your eye on the leaves and make sure they don't start to turn pale green / yellow (don't worry too much about the very top shoots as they often go pale in strong sun), or develop brown tips, margins or spots. If so your plant is probably hungry.
Also does your pot have holes in the bottom? This is important so the roots don't get waterlogged. If it doesn't, you need to re-pot. If it does have holes, are there any signs of the roots coming through? If so, again you should re-pot to a bigger pot, at least 10 or 15 litres. All of this will help to make sure your roots are doing their job and getting plenty of food and water to the stem and leaves.
You won't know the sex until it starts flowering, not for another 4 to 8 weeks possibly. The FAQs have info on how to check.
Sorry this has been so long. Come back if you have any questions. I'm a beginner myself but you have to learn fast. If I don't know the answers I'll try my best to find someone who does.
greenb.