Aww, it sounds like you're in a similar boat to where I was. When I got my Galah she was very underweight, her poor keel was sticking out so far and her chest was a V shape. I didn't realize that wasn't normal right away because as long as I've known her it was always that way D: It didn't help that my mom didn't feel that it was important and told me to just let her gain weight(I didn't have a job at the time because of college).
Here's what I did for Rosie
When I first weighed Rosie she was barely 250 grams, I started feeding her lots of different foods(she loved the muffins I made her) but her weight would fluctuate a lot between 250-265.
With the fresh foods I decided I might be overwhelming her with the variety, so every two weeks I would add a new food to the mix(carrots, apple, cucumber, spinach). I also tried feeding her hard boiled eggs, fish, cream of wheat, oatmeal, pasta and noodles, and walnuts(she dislikes almonds) and much much more.
I wanted Rosie to eat pellets, but sadly she picked around them and continued to mostly eat the safflower. To combat this I decided to buy the fiesta conure sead mix and after picking out all the sunflowers gave her that each day. I chose fiesta since it has a variety of pellet like objects that where colorful. Once I noticed she was starting to nibble on those I decided to add two new pellets to her daily mix. One was Lafeabers while the other was zupreem natural. She was starting to eat more of the pellet, then for Christmas my friend gave her one of those fiesta cardboard seed toys you hang. She completely ignored it for a month until I started lessening her amount of seeds then she slowly started nibbling on it.
I'm really sure how this happened, but I had to leave for a weekend and when I came back her seed toy was almost completely gone and she was now eating her pellets perfectly and nibbling her fresh foods more often. I think she finally realized the pellets aren't that bad.
Now that Rosie was on pellets she suddenly started consistently gaining weight little by little. Now she stays at 280 grams and is much more energetic. Once I got her on pellets I started removing the zupreem pellets since they aren't true pellets,(they were mixed together to give her the most variety and hopefully make it more interesting.) After that I was told by my vet to feed her Harrison's but she refused to eat it and after 3 bags I gave up and looked for a good alternative. I ended up choosing Totally organic and which she eats everyday and since then her character has changed and she's a very happy bird now.
I've had Rosie since august and I finally have her where I want her to be. Just getting her on pellets which was the break through for her weight took 6 months to do. I barely recognize her from the bird I brought home
