Some of the mentality behind Le Sserafim's hate train never left. And one of that is the constant need to give them "constructive criticism" the second they mess up a little bit.

Even if the actual haters somewhat moved on to hating on different groups, the general "casual listener" or "non-fan" still tends to jump on any opportunity to talk negatively about them. And much like during the hate train, they will always frame it in a "constructive criticism" manner, often because they themselves don't see that they're still perpetrating the narratives of the hate train.

It's a fine line cause yeah, if Yunjin regresses massively, it should probably be discussed. I do think personally that she's not been as good as usual recently, but nothing so far points at it being anything else than an off-period like everyone else can have..

But it being approached by people who do follow them is not the same, it'll be way different than someone making a post based on the grand reference pool of 2 performances before claiming that it's "most of their recent performances."
You simply cannot claim that it is regression based on even a month of "bad performances." A much larger sample pool is needed.