What's going on here?

Hola. I assume there's just something I'm missing here, but hoped someone could point out what that might be;

I'm on level 6633

and keep finding myself in this predicament:

Where I'm left with X-number of non-existant Bubblegum targets(?) I don't see any method of generating more? Are they self replicating? I would think that if it were a circumstance where I'm dispatching of them too quickly I would be given the old "Oops" no more objective targets available prompt (which hasn't occured).

Scratching my head on this one...