Grout line that is along the counter top (behind sink) is shrinking and creating a gap. I remember when the counters were installed the wall were NOT square so there was a gap between the wall and the counter in this area. My instinct is that the grout wasn't pushed in far enough to fill the gap and now that it is shrinking the grout is just falling in behind where the gap is.

My question is. Does it make sense to remove all the grout behind the sink and re-grout making sure to push extra hard to fill in the gap or should we just remove the grout and caulk it. Also, if caulking is the way to go......is there different color shades to attempt to match grout.

Please help me.