Cynlinder 1 injector offeset is learning at min limit, what does that mean?

Question

Cylinder 1 is also miss firing, I plan on changing out the glow plugs on a 2011 BMW 335D.  I also planing to walnut blast the in manifold intake and add a catch can?  Should I have the #1 injector check to be replaced?  And if I replace that injector, should I replace all of them at the same time?  The car has over 90K miles,  I don't think any of this has been done.  We bought the car used and had some issues since we bought it, I have been able to fix them.