Different varieties of chilli come from different areas of the world. Central and south America, India and the far east to name a few. Some varieties will need hotter, drier growing conditions, some will need cooler or more humid conditions.
Keep with them, they might just be a later variety.....I have 20 different chillis and they're all at different stages of development.
Oh....whetever you do....don't feed with tomato food until they set fruits. To be honest, I would only feed weekly with half strength general purpose feed such as miracle grow.