What does your diet look like? Give us a general breakdown. If you’re looking to add mass to your tri’s, you’re going to have to gain some weight.
You and I have both been training seriously for about a year. In that time I’ve gone from 170lbs to 205-210. If your pics are any indication, you’ve been at a caloric deficit for a while. It’s time to step it up if you want to add mass.
You obviously have the discipline and work ethic. Feed it and it will grow.