For your weight, I don't think it's enough calories. You probably threw your body into "starvation mode" temporarily (and I think you probably lost so rapidly due to water weight! According to
www.caloriesperhour.com and
www.freedieting.com, your BMR is around 1700...which means you need at least that per day to live...factor in exercise, and you'd need more just to maintain. I would incorporate more healthy fats - olive oil on the salad, perhaps? How about some flax in the oatmeal? Or, with the apple, you could have some peanut butter or soy butter (or a pita & hummus!) Also, maybe add a starchy veggie or carb to dinner. Brown rice, couscous, etc. If needed, why not add a fake "dessert" after dinner? Low-fat yogurt. You barely get any dairy servings!
Bfast: Oatmeal and glass of soy milk
- Add some nuts, or stir in some flaxmeal for fiber & healthy fats! Could you add some egg whites or something? Protein is really good in the morning. I personally hate meat at breakfast, but I do cottage cheese or nuts.
Snack: Apple or grapes
-Again, you could add a small serving of nuts or dairy here. String Cheese? Granola?
Lunch: grilled chicken salad with salsa
-I'm assuming you're using the salsa as your dressing - why not use a healthy-fats dressing (sorry, I don't eat salad, you may need to ask someone about that). Again, nuts are good...like walnuts. Turn it into a fiesta salad with some beans...or crumbled tortilla chips. Or go asian with some orange slices and sesame seeds!
Snack: granola bar or fruit
-You could get a higher-calorie granola bar (I don't know what kind you eat, but Kashi is ALWAYS a good choice!) or add some cream cheese dip for the fruit...some nuts. Or a glass of soymilk.
Dinner: chicken, steak, or salmon with veggies
-Add some whole grains here! You get plenty of veggies and fruits throughout your day...time for some good whole-grain stuff! A whole-grain roll, brown rice, lentils, whole-wheat noodles, couscous. The possibilities are endless!
Just my 2 cents.