The pictures are a little blurry, but I have a group of Sri Lankan stars and can easily sex mine, even at four inches. Can you post a couple clearer pictures? Yes, it will continue to grow on a daily basis, as yours is only four inches.
This star you are showing is just too young to sex. I have had animals that were 2-3 years old and I would have sworn they were females and it was almost like overnight the tails grew and now I clearly have males. It just comes down to, that a 17 month old animal is just too young to sex, unless you know 110% sure what temps the animal was incubated at, and then you can make a better guess at this age, but honestly its just to soon either way. Good luck with him/her and enjoy growing it up!!