First of all, if your friend is using MG soil it may have those time release pellets of fertz in it. If you or your friend see those little colorful balls of green, yellow, red, and blue then you have the MG time release fertilizer soil that's bad for growing cannabis. I say this because MG time release fert soil releases fertilizer with every watering causing nute burn of your friend's babies. Also the pH of the soil could be off causing your plant to be unable to absorb the nutes it needs which shows up in this way (i.e. deficiencies). How often does your friend add extra MG fertz? How often do they water? What kind of MG soil? Also what kind of a set up do they have? Lights, etc? The more information you can provide, the better we can help you and your friend