Is losing 5 pounds every 3 days unhealthy?

I'm 14 and I'm a vegan. Every day for breakfast I eat an apple, piece of toast, and a liter if water. For lunch I'll eat raw vegetables or fruits and another liter of water. For dinner I'll eat some source of protein other than meat and another liter of water. At the moment I weigh 134 oz. and I'm 5'7. Is this unhealthy?

you are at a ideal weight for a person at our age (im 15) but remember that you need vitamins and sertain other things from meat that veg, and suppliments canot give to you. be careful in that regard. I suggest you eat more for your dinner, considering you have at least a 5-7 hr fast while sleeping. never skip breakfast! its good that you eat healthy items tho so good on you for that. but in all, it sounds like a normal weight for your height and age.