Honestly, red suffusion could be caused by more than a bad diet and liver issues. Sometimes it resolves itself with proper diet and supplements, other times the birds die. Some birds feathers will return to normal, however the bird itself is not normal. I've seen this in a green cheek conure.
Here's red suffusion in a lutino peachface
http://www.angelfire.com/rings/ringcage/kuya/thumbnails/400x300/Red_Suffusion.jpg
Red suffusion progression in a normal peachface lovebird. Unfortunately, even with testing, the owner was not able to figure out why her lovebird had red suffusion, and her bird ended up dying (she was put under to get blood to test for PBFD, but died while waking up, accidentally getting aspirated). All her organs tested normal and she tested negative for PBFD. Before this lovebird passed away, she became even more red, started losing feathers and weight.
http://i29.photobucket.com/albums/c268/baby_geek/ZoeyFront.jpg
http://i29.photobucket.com/albums/c268/baby_geek/ZoeyBack.jpg
And photos of a green cheek conure. No one knew for sure what she was when her owner first got her, and I was the only one who assumed she was a normal green cheek conure. This particular conure feathered out normal, but acted "drunk' any time she tried to fly, so had to be clipped for her own safety. Hopefully, the images work
http://board.birdchannel.com/Uploads/Images/55c00433-d563-4c20-b0a4-4183.JPG
http://board.birdchannel.com/Attachment581.aspx
http://board.birdchannel.com/Attachment582.aspx
http://board.birdchannel.com/Uploads/Images/c97a47fc-3017-47fc-83a9-696b.JPG
http://board.birdchannel.com/Uploads/Images/21b81bba-e1c7-44fa-9c1e-1fc5.JPG
http://board.birdchannel.com/Uploads/Images/5b625f7a-e951-4603-a672-a063.JPG
Red suffusion can affect the entire body or only parts of it. Usually, if the red disappears, this means that the bird will probably survive. However, if the bird keeps gaining more red feathers, and never loses them, it's typically an indication the bird will die "soon." Soon could be several weeks, months or even a couple of years.
I've also seen red suffusion in princess parrots, although there may be two versions of it... some will molt in red during breeding season then molt out to normal colors in the off season and the birds are unaffected. However, the other red suffusion (i.e. health problems) can also affect the feathers. Below is an image of a red suffusion princess parrot with confirmed liver failure/disease
http://www.auspigeonco.com.au/melbournebirdvet/photos/large/(21).jpg
Liver failure, if it affects the feathers, will make the feathers turn yellow, red or darken (if the other two colors are not present).
Red suffusion = not a mutation and cannot be reproduced, unless it's a genetic defect
Red Factor = mutation and can be reproduced
It's good to know what to watch out for, but at least you wont have to worry about your lovie for now!