Heater Core - Weak Spot / Leak?

Car: 1986 328 , 76,000 Mi

In the middle of heater hose replacement and pulled out the cores to route hoses under dash, clean cores and replace filter material.

See photos below. Looks like possible coolant stains near where the hose nipple passes through the cutout of the core "housing." Does this in fact look like a leak / impending failure? I only want to take these out once... Would like to reinforce / repair now if this is going to be an issue.

Notes:
1. Plastic boxes containing cores do not have stains, so it's a small sweat if anything at this point, not a full on leak.
2. The stain is located on the outside (closest to the fender) edge of the inner (closest to heater value) nipple. It's the nipple that connects to the valve. You know how that hose (core to valve) does a 180 degree bend as it connects to the heater valve...? It seems it might naturally push the nipples toward the outside (toward fender) edge as the hose tries to spring open... Are these nipples being forced to rub against the housing under the pressure of the bent hose? BOTH sides show this exact sample pattern....
3. I assume the housing is steel, so copper against steel (galvanized?).

Would love to hear thoughts, suggestions and experiences...
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Is there any evidence of the valve leaking and allowing coolant to weep along the hose to the stain you see?


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If you are talking about the white areas, are you sure it is not excess flux from the soldering. Assuming it is silver solder, the dry flux powder is usually white in colour, try a fine wire brush.

 

1. No indication of leak from the valves along the hose. Note: when I turned on the heater to drain the system. The driver side LED only went half way up the light chain on the switch. This is unrelated, but interesting. Thinking of a way to test valves while I have them handy..?
Could be switch calibration? There is a TSB on that...

2. So, with a brush, I would be cleaning the powder away and looking for a solder joint / bead under the residue...? If none, then might mean this is fluid. Any known way to reinforce this area while Im at it. Perhaps it's strong, but my replacement (Gates Green stripe) hose has thicker walls and the hose bend will apply more pressure for sure than OEM..
Thinking of a way to make a contour brace for the hose to prevent pressure... Or maybe find a 180 degree elbow that could work..
Am i overthinking this...?

 

Its a bit difficult from the pics to fully understand this to be honest- i have not seen 1 of these apart on the mondial i had

 

Assuming i am seeing this right, has the solder cracked where the bracket is attached to it ?