yes to me it looks like common or garden (on heavy dampy ground ) redshank .easy to kill if it is even a top or 2 will as its an annual.I'm starting to think it's called redshank / jesusplant
24d is a chemical2,4D? RBH? I'm sorry I don't know what those are
The area in question is wet for a few months of the year. The field was sprayed with Mortone a few years back for rushes, it put this unknown weed back but didn't seem to kill it.