EAGLE - how to make ground planes to connect to the smaller PADS
It's a bit of a quirk with Eagle, but a polygon has a "width" associated with it, just like any other track. It sets the width of the aperture used to "paint" the fill inside the polygon. If this width is too large, then it can't paint the path to closely-spaced pads, as you have found.

The fix is to set the polygon to use a smaller width. This allows the polygon to flow into tighter spaces, before it gets blocked by the clearance rules.