Heya thanks ya’ll for the comments and suggestions. I tried out my ancient pair of Etymotic ER-4s(the red and blue one) on the same songs and also hear some sibilance too.
I’ll try EQ-ing.(theres a first time for everything right!) I also have the Moondrop XLR cable on the way from the online shop, will share if it makes any difference.
Update: interestingly when I used the 3.5mm copper cable with 6.35mm plug, the sibilance is less. I’m using the same k9pro Ess on high gain. Previously I was using only the 4.4mm SPC cable provided.