Electrical – Ceiling junction box has 6 wires

On my kitchen ceiling, there are two light boxes controlled (I hope?) by one dimmer switch. The boxes are connected to the far wall (opposite the switch) by a conduit that runs along the ceiling; however, some wires stick out directly from the ceiling, not from the conduit.

               add'l wires 
  ____________||________||_____c_e_i_l_i_n_g_______
  |]========[boxA]====[boxB]                      |
  |      ^                                        |
  w     conduit                                   w
  a                                               a
  l                                               l    
  l                                               l
  |                                               |
 [|]                                              |
 [|] <- breaker                       dimmer ->  {|
 [|]    panel                                     |
  |                                               |

Box A only had two loose (capped) wires: a black and a white. I tied them to the respective black & white wires of a pendant fixture, and all was well. That light is now controlled by the dimmer switch exactly as I'd expect. For the sake of completeness, I'll note:

• There was another pair of black Romex running thru box A, but it didn't have any ends exposed, just ran straight thru the conduit toward box B.
• Box A doesn't appear to be grounded? I ran a green grounding wire (which came with the fixture) from the pendant's canopy to the junction box, but there's no connection to the condo's ground wiring that I can see.

Meanwhile, over in Box B, I found a total of 6 wires, which were joined together into 3 pigtails.

1. Black Dark Grey + White
2. Black + Black
3. Blue + White

There is continuity between the black grey wire in pigtail #1 and the blue wire in pigtail #3. (Note that these are the two wires coming from the conduit; the other four come from the ceiling). No continuity between any other pair of wires.

So, questions:

• How the heck do I wire my second pendant fixture into box B?
• Does the wiring in box A need to be modified for proper grounding?

Edit: here's a zoomed out photo

^^ From left to right, you can see the wires coming out of box B, the pendant successfully hanging from box A, and the breaker panel underneath the shelves on the far wall. I separated the box B wires for testing (i.e. the pigtails seen in the closeup photo above are no longer connected), so the pendant obviously does not light up anymore.

Followup Edit: by popular request, I've disassembled box A for photographing, and taken a bunch more measurements.

^^ Here you can see the single black and white wires coming out of the ceiling, which I'd previously wired into a pendant, and also the conjoined pair of wires (black+grey) running thru the conduit. As for continuity:

• Box B pigtail #2 black [the one paired with black] == Box A's loose black wire
• Box B pigtail #3 white [the one paired with blue] == Box A's loose white wire
• Box B blue == Box B dark grey == Box B ceiling plate == Box A ceiling plate

The main discovery is that with better lighting, I can see that the dark wire from Box B's first pigtail is ever so slightly lighter than the other two black wires. I've relabeled it "grey" above, since it appears to be grounded.