Sprite Atlas blurring on downscale from UD to HD and SD

Hello so originally I was working on with SD graphics in the game i.e. 1x resolution.

New Assets were created at 3x the size and were to be used instead now, sprite atlas was to be used to created downscaled 0.33 and 0.66, i.e. 1x and 2x for SD and HD versions.

For SpriteAtlas main i have simply packed my spritesheet that i created from texture atlas, i started with one of the objects in game to see what kind of effect it has in my game.

so immediate reaction was this.

https://puu.sh/ygJn1/8862faa87d.png

the sprite went 3x the size, which is to be expected since the graphics are 3x size now.

on playing with SD variant of sprite atlas included in build i get something like this

https://puu.sh/ygJoi/f0338408f8.png

a super blurred version

ofcourse since the size in game is 3x now, i tried increasing size of orthographic camera so that the size of bird is same as how it was before and then included in SD variant, but still the result was a blurred image

https://puu.sh/ygJr5/c39579bfab.png

so my question is how can I do what I want to do? is it possible to use SD, HD, UD variants but not having to increasing the orthographic size, which will also lead me to reassign colliders (since size would have changed), if this is the only way what can I do so that things dont get blurred.

the original 1x images are not blurred btw.

Thanks