The image aspect ratio varies

I have placed three photos on Blocs site. All images are same size and same aspect ratio. But measurements in Blocs are not the same anymore. From left, first image is 370 x 524 px, second is 370 x 556 px and the third is 370 x 526 px. What is happening here; why all images have not the same aspect ratio?

I continued to investigate the matter. In the first time when I have exported the images from Lightroom (4) the aspect ratio was same in all images. The value of width was 800 px. But the height of images was varied after placed the images into Blocsapp.
Now I made the image exporting job in the Photoshop and the width value was 1000 px. Now the image aspect ratio was the same in all three images also after placing the images into Blocsapp!
But still I don’t know what was the issue in my first try!
Made the third exporting from LR. In the first time I have exported the images one at a time. But now I exported all three images all at the same time. And now also after placing images into Blocsapp the width and height are same in all three images.