And check the interior of the BIX I , that was also in the same loop as the blocks.
Hard to tell what's solder and what isn't there...

My Swiftech blocks all ended up the same as yours despite running 10% Zerex / 90% distilled and flushing/refilling with fresh mixture every 6 months... MCW462, MCW5002, MCW20, MCW40... all the same... DD original Ali Top'd Maze4 likewise... Innovatek Rev3 CPU Block likewise...

All anodised... anti-corrosive additive used precisely to manufacturer's mix ratio for proper protection rather than clear-tubing... all still corroded within 18 months. The swiftech blocks ended up with corrosive pits around half a mm deep iirc... s'why back then I went with dangerden - no aluminium used at all...