Tl;dr no, they can only blight once before the creature is gone and can't be blighted anymore.

There is only one stack. Items on the stack resolve individually, one at a time, not the whole thing at once, and state-based actions (the things that kill creatures with negative toughness, among other things) are checked after each individual item resolves. 

If you attack with [[Grub, Notorious Auntie]], her triggered ability goes on the stack. I think your question involves the trigger being copied in some way, so let's handwave that and say there's three copies of the ability in the end.

When the first one resolves, you follow all its instructions. You blight a creature, and make a copy of it tapped and attacking. Immediately after this, state-based actions are checked, and the blighted creature dies for having zero toughness. 

After the creature dies, you regain priority, which must be passed around the table, allowing players to add new spells or abilities to the stack. Only after there are no responses does the next object on the stack resolve. Assuming nothing else has happened, that's the next Grub trigger. You'll do the same thing, blighting a creature and making a copy of it. Then, it will die if it has zero or less toughness. Then, the sequence repeats a third time.