Look at the basics

Is your water good ? pH, no chlorides, ppm correct for its growth? How much do you let it run off? 

It's outside are the temps good? Sounds like if your friends are doing well the temps are ok.

Have you compared notes on your techniques with your friend? Just asking since you said their plants are well and yours not so much

Look closer at the basics light, temp, water quality nutrients should not be a concern if your in soil.

Hope this helps