It’s definitely the fluorescent causing it to turn icy blue. I almost bought a ring with very strong fluorescent and didn’t dig its look in the sun. Ended up getting one with no fluorescent. Although may appear more tinted without the fluorescent since it’s a J, No regrets.
Original stone 1.7 J VS2 with very strong blue fluorescent in direct sunlight around noon time
Same ring in the shade
New stone that we purchased-1.67 J VS1 with no fluorescent. The stone turned a deeper but more opaque blue, more reminiscent of a reflection vs full transformation of the diamond into blue.