Welding Rod brands DO make a difference: see this testimonial about a 140ST.

[welderdude]

I gotta wonder if the box had been dropped. It doesn't seem to take much to do some damage to a box of 7018s. Were the rods sealed in a plastic bag? One other thing I notice, although I doubt it makes a difference, is that they have the -1 suffix, which means the welds are more impact resistant.

Also, by finger-nailing, you mean that a chunk of the flux sticks off the rod and doesn't melt, therefore causing it to long arc and/or arc out the side?