well im using soil, it just started showing sex like a week ago and im using foxfarm nutes once every other watering and its happened to like 3 different sets of leafs
what lighting? some leaves naturally yellow and fall off, if light doesnt reach low enough in plant lower leaves will yellow and die. nitrogen deficency will do the same thing, and bad ph can cause similar problems
it is hard to say without pics, you have to answer more questions. what type of light and wattage? what is your ph? how strong of dose are you giving nute wise?