I recall hearing of the chair of a department giving every student an A. For multiple quarters, every student or nearly every student got an A. (I was fortunate to be one of those students.) We were a small class, just 8 students. Many of us has significant background experience, some professionally. (One common trait, though, was that we lacked educational degrees in the field.) She spoke to the dean.
She said, "these students do deserve it."
She fared well. The next year, she got more students, and those students got different grades.
I'm glad she defended what we rightfully earned.
Later, I became a college instructor. The college was giving As to nearly every student. Yet, they were not being masters of their work. I started creating my own quizzes/tests/exams. This resulted in lowering some GPAs. I didn't feel one bit guilty about that impact, because the GPAs were previously higher than what was rightfully deserved. (That was still an issue after I started making the gradual change, but at least it was better. Since there was some grumbling/minor uproar from the shock of what was being implemented, I didn't feel like I was moving too terribly slowly at addressing the issue.)
The only good way to lower grades is to let students be aware of what standards are, and adjust standards. Anyone who successfully meets standards ought to get an A. Anything else is not right/honest. If too many students are meeting standards, then adjust standards early enough that the students have time to adjust, or just give them the grade that they earned and make adjustments to try to do better for the next round of students. Don't deprive anyone from what they deserve.
Don't wimp out due to fear of meeting a dean. Someone (possibly the dean) will respect your willingness to meet a challenge in order to do the right thing. Cowering behind the apparent safety of avoiding the meeting is more likely to haunt your conscience years later, after the situation is clearly unfixable. Always do your best to do the morally right thing.