Ask yourself, have you been true to your workout? If that is in place, then look into your rest, recovery and nutrition. If they are in place too, then sometimes the central nervous system is fatigued and requires rest due to over training.
Is it true that some people naturally lose weight faster than others?
Yes, there are many factors but the main two are predisposition to stress, and metabolism.
The first one is (in non-nerd speak) the way someone reacts to stress. People will either eat more (comfort eaters) or eat less. In this busy world, stress plays a major role in body composition, and whether a person is a comfort eater or food avoider when stressed will determine their predisposition.
Metabolism (in my opinion) is secondary.
If someone has a high metabolism (uses more energy to stay alive) then they will naturally lose weight faster than a person with a lower metabolism.
Age and gender are the major contributing factors to metabolism; a younger person has a faster metabolism than an older, and a man would have a faster metabolism than a woman.
In saying that, of every 100 people who lose weight quickly, 99 will put it back on. Consistency is far more important in a weight loss journey than speed.