Before you nuy something you dont need, that discharger you have is for large packs used in electric rc's, not rx packs.
Check all your connections and wire make sure everything is plugged in correctly without any debris that can cause bad connections, or frayed wires.
If that doesnt work go down to your LHS with your truck and controller, and ask if you can try a different set of crystals as long as your hobby guy isnt s total ass he will let you try them before you buy them. If that fails, ask your hobby guy.