when you use nutes you need to start out at 1/4 strength. So instead of the 1tsp (5mL) it should be a 1/4tsp (little more than 1mL).
And you only want to use nutes when you know the plant is ready for them. They need to establish a good root system first. Once you feed with nutes for about 2 or 3 weeks you can up the dosage to half strength. Your plant may have nute-lockout, which means the roots are damaged to the point where its hard for them to suck up the water and nutes, and they eventually end up dieing. I say start flushing with just plain pH'd water for a little bit and see what happenes.