The symptoms you describe are sign of file corruption and data loss. That's a case of silent data corruption. It's silent because it don't generate any error message when you read the file.

It appens when part of the file get lost. If the top and bottom are missaligned, that means that bits from the middle of the file are missing.
If the gray area cover part of the image, it means that the file have been trunkcated. A BMP will lose the top part. A JPG, GIF, PNG and others will lose the bottom part.

Unless you have another copy of the affected files, there is no practical mean of recovering your photos.
By practical, I mean that won't cost you an arm and a leg, with no guaranty that it will be successfull.

What you MUST do NOW:
Take all the files from your drive(s) and copy them somewhere else.
If the image only have a small gray stripe, using a graphic manipulation programm, crop that stripe out.
If the gray area is to large, you'll have to resign yourself and delete the to corrupted image. Sory about your loss sad