i'm new and i could be wrong, but:
i read in some book that people tend to think that fertilizer is the only source of a plant's food. but this is not necessarily true. plants make their own food through photosynthesis.
fertilizer is just a supplement.
with that in mind, you probably won't kill them by under-fertilizer. but you'll definitely burn them up if you over do it.
when in doubt, i would just wait or dilute.
and here is a great article on what happens if you over-do the fertilizer:
http://www.aos.org/AM/Template.cfm?S...entDisplay.cfm