Foliar feeding is your problem. Don't feed this way - it's not dependable, you don't really know whether it's the right amount. You wrote something about foliar feeding with more than one kind of fert. Why? That's asking for trouble. If you grow in potting soil, one thing you can do to make this work is go with a fert that dissolves in water and just water with the fert/water mix if you want. You can measure pH but I wouldn't worry about that too much. Maybe take the TDS/PPM measure up to about 1200 or so as they grow. I'd stop the foliar. You say the fan leaves have turned brown which is a good indication of either heat stress or too much fert, typically speaking.