I hope your growing season is going well. You might want to take a look at the sixe of pots that your chillis are in, as a general rule a chilli plant will grow as big as the pot it is in. Here at Fire foods we start off in small polystyrene cups, then 1 ltr pots and finally buckets that we get free from Asda, just ask at the flower desk.
Your chillis will also need regular feeding, for this any tom feed is perfect, or you can make your own, just pick loads of nettles, add cold water, cover and wait 7-10 days, by this time you will have a dark liquid forming, this is also perfect food for chillis.
I never pinch the tops of my plants but you can to get a bushier plant. Happy growing, and if you have any questions about your plants please join our chilli forum here