The quarterly financial results of Big Tech (MSFT, GOOL, META) did not have the same momentum as before, with the real sales growth rate after adjusting for inflation in the single-digit range.
This means that it is weakening to rising interest rates.
On the other hand, looking back at the FOMC the other day, it seemed that Chairman Powell was becoming optimistic about the outlook for the economy, such as deepening his confidence in a soft landing.
Since this is a factor in the rise in long-term interest rates, I think it will happen that “Big Tech's stock price will begin to decline even though business performance is strong” in response to a decline in valuations.

Tonight's stock depreciation is not affected by the downgrade of US bonds, but is due to the fact that the number of people employed in the non-farm sector in the ADP US Employment Report in July increased by 324,000 from the previous month, which exceeded market expectations of an increase of 175,000.
In other words, since the US economy is too strong, long-term bonds are being sold, and stocks are depreciating because they are disgusted by the rise in long-term interest rates.
Even if Fitch downgraded US bonds to AA+, I don't think it's particularly surprising since S&P Global changed it to AA+ 11 years ago.