hmm, it is outdoor, you giving them nutes or what? what are you giving them if anything besides water.
been doing outdoor for more years than i want to count, not once have i ever used more than just Water. and the Soil god gave me, and it always turns out superb.
Just make sure you love the shit out of them.
But without more info it probably could have been a variety of problems, from tiny bugs, to anything else.