Do a search on bonsai and you will find a thurrow artical I posted on here. But if you don't, then just cut the tops, next time keep them in small pots and don't keep them close to your 400W. Keep them on the side or approx 2FT away and after you take cuttings just put them back up to it for a few days and it will help to premote the new growth faster. Also, feed low amounts of N except after cutting or just get something like some Shults 20-20-20 all purpose potting soil and just plain water and change soil out once a year and only feed nutes if they show defs.
Adieu