yea, sounds like you've got some tall skinny plants, probably not receiving enough light and stretching up to much. More wattage will help with stretching. An oscillating fan will help with the thickness of the stem. You can rebury the stem with more soil, right up to the first set of leaves if needed. There is also a thing called dampening off, and it will effect young seedlings, eating away at the base of the stem making it very weak, When any of my seedlings get dampened off I will just scrap that particular seedling.