Hey mate,
Get a moisture meter for the soil... I think you are watering too much and that's why your leaves are drooping.. If that is the case, the soil moisture meter will help you to see when you want to water... just as the soil is going dry from moist. You will notice your leaves lift up and look a lot more vibrant. Hope this helps you out. Good luck.
Also, as far as nutrients go, I find nutrients in a few stores where I live that are not Hydro stores. I find some nutrients in big hardware/garden stores. I'm not in the US so I couldn't tell you what stores you have there.. In OZ we have Bunnings (I don't buy there although if I couldn't buy anywhere else it would be a last resort, they stock boost juice, canna a+b and quite a few other things in Bunnings).
Skroatz