Some icons look blurry under HiDPI

[ghost]

I'm using a 13-inch 2160*1440 display and scaling factor is set to 'Pixel Doubled'(200%). Here's what urutau and elementary looks like in comparison:

• elementary
• urutau

Notice that:

1. The border of Multitasking View icon looks more blurry in urutau, and it's the same with Vim icon. Meanwhile, the Remote Desktop icon, with the similar blue border, looks just fine. There's an inconsistency in there.
2. The Telegram icon is a bit of smaller compared to both the original one and and other icons in urutau.

Here's one more example of urutau icons: You can see urutau icons(DOSBox, Fcitx in this case) are definitely more blurry, especially when compared with those using their own icons(Alias, Locksmith, I think Multitasking View is also using its own icon in elementary theme). Since my screenshots are not scaled, you can also tell that Telegram icon is a bit more tiny than Chrome.