Ok there is so many variables that nothing is really absolute, are either one of your buddies running the same light and setup as you ? and are they growing in coco , coco can have it own issues especially if its not buffered correctly but your in flower right ? my question would be are you sure your getting enough runoff to control EC in medium and are you controlling dry backs properly, and have you checked root zone PH. Honestly your nutes could have been locked up or under fed without being there or seeing it its hard to say. are your root healthy, what about the rooms environment? your buddies are telling you 2 different things because there rooms may seem the same but be a lot different, no what I mean. make sure all your basics are covered plenty runoff, EC out PH in and out, make sure environment is as good as its going to be temps, RH etc all that stuff, if all those are good then look at EC because 3.0 is not set in stone. how far a long in the grow are you ?