It's kind of hard to tell a lot from these pics, but I'll give it a shot.
I don't think your Fawn is a Yellow Beak. Female Yellow Beaks have a more obviously yellow beak. In general, among the same colors, females will tend to have a paler beak than males, and younger birds will also have paler beaks. I haven't seen Yellow Beaks in-person, but all the pics on the net show a much clearer yellow -- about the color of a Masked Finch's beak. You might be seeing more of a difference from the others because the others are boys and she was the only girl. But, again, it's hard to tell from these pics.
Your male that "looks like a normal but a little softer" might be either a Light-Back or a Dominant Silver. If you had a pic of him I might be able to tell better, but those are two mutations I can think of that have a dilution effect without much change in pattern. In any case, because they are different from Fawn, if you used this male, the offspring will not be Fawn unless he also happens to be split to Fawn.
If you really want more Fawn but can't find any others to buy, could breed your Fawn female to her father. Doing so, half the female offspring will be Fawn and the other half not, and half the male offspring will be Fawn and the other half split to Fawn. Breeding a Fawn male to any other color will give you Fawn daughters, so you'd have to inbreed only until you got a Fawn male offspring, and then outcross to an unrelated bird.
Or, you could breed any other male to her. The sons will all be split to Fawn. If you bred one of her sons to any other female, half of the female offspring will be Fawn. You won't get any male Fawns this way, and not all the females will be Fawn, but it's another way. To get a male Fawn, you'll have to breed a Fawn female to either a Fawn male or a split to Fawn male.
Flip through the varieties on the web pages below and see if you can sort out what you've got. And look at the pics of Yellow Beaks to see if you agree with me about that.
Edited by AquaEyes - 4/22/12 at 7:16pm