Clinker/facing bricks ruined by GÜ!

Last summer, we built a "turnkey" single-family house with a local construction company (as general contractor). A rather expensive clinker brick from a well-known manufacturer was chosen for the facing façade of the house and garage, and these were subsequently darkly pointed. The visual appearance of the property looked really great!
A few weeks after pointing, some black streaks appeared on the clinker on the west side. Through our own research and the involvement of our construction expert, this indicated contamination or faulty cleaning (e.g. with acid) of the clinker. We also brought in a "representative" of the brick manufacturer, who verbally confirmed this to us. Subsequently, the affected areas were cleaned again without success by a subcontractor of the general contractor.
In the acceptance protocol, these still visible streaks were noted with reservation, since replacing the bricks would probably have caused an even worse clinker image including pointing.
Now, after the first very rainy winter, strong discolorations (rust-like) and some efflorescence on clinker bricks and joints are visible on the entire weather-exposed side of the house and garage, as well as on some parts of the north side. In other words, the damage has massively worsened. Apparently, acid was washed out of the joints by the rain, which penetrates sideways into the clinker bricks and triggers rusting of their components there.
An initial defect notice was rejected by the GC with the reasoning that these are normal processes on the weather-exposed side that do not constitute a defect.
The bill of quantities of the GC contains an item "Cleaning and acid washing of the facing bricks." According to the clinker manufacturer, these stones must not be cleaned with acids, which probably no longer corresponds to the generally accepted rules of technology.

Now our questions to experts or possible fellow sufferers who have experienced such a case before:

[*]Is it to be expected that the other clinker surfaces will also discolor and effloresce over time?
[*]Some companies advertise that such damage can be removed by later cleaning. What is your opinion on that?
[*]Could a laboratory analysis of a milled-out clinker brick and joint mortar provide insight into possible faulty cleaning or manufacture of the clinker brick?
[*]To what extent is there a distinction between functional and optical defects with regard to warranty or damages?

What further course of action is recommended?

Greetings from Heidegeist

In your case, I would take an expert who is familiar with Verblender !!! Usually, your clinker manufacturer could name a person for this. But one thing I would argue: All manufacturers say: do not use acid! But if you can prove it (you can have it examined), then the processor has made a mistake. What else could you do? Have it given to you in writing how the clinker was subsequently cleaned by the subcontractor. I think this is stated in DIN 105, when one speaks of a real defect, the entire area also plays a role, but the expert will tell you exactly. I wish you good luck, hope I could help you somehow!

Thank you very much for the response

That sounds like a viable way. We will probably not be able to avoid a laboratory analysis of [Klinkerstein] and [Fugenmörtel]. But then the matter would be relatively clear, provided it was treated incorrectly.

Greetings from [Heidegeist]