We'll need a little more information please:
Are you growing in pots? If so, what size.
If you are growing in the ground, please tell us about your soil
What variety of jalapenos are you growing?
Is your tap water chlorinated?
How far do your plants get before they fail? Do they flower?
When you say plenty of sun, how many hours of direct (nothing in between the sun and your plant) do they get each day? How many hours of indirect sun?
And any pictures would help.
