Why do my tile textures keep resampling/blurring?

Question

I set up a tilemapnode in my gamescene.sks file and the tiles are 16px by 16px but are scaled up to 128 pixels. They look fine at first but if I start editing or adding new tiles later on the old tiles get resampled automatically and look extremely blurry compared to the new tiles. Any idea why its doing this and how to fix it?