There was an issue in Mylio, introduce in iOS 9.3 (apparently a change in iOS, and something Mylio had to play catch-up with), where any photos shot on an iPhone in  portrait (vertical) orientation showed up distorted in Mylio for iOS. The fix is in, but you have to do something tricky to get your images as they should be.

The short version is; in the Finder in OS X (or Explorer on Windows), you need to move the affected photos OUT of the folder they are in, to a folder that Mylio doesn't watch… wait for Mylio to recognize that they are gone… then put them back again. 

The caveat is that while your edits will be saved, since those are kept in an xml sidecar file, if you had organized these photos into Albums, they will be lost from the Albums.

Here's a quick video of the tip in action.