Ignoring the Dip discussion.
The problem you may be experiencing can be your diet, your "overall" training, potential genetic connection, and possibly length of training (etc, etc, etc).
You say you have been
busting up the iron for more than a year (I assume consistent/constant), and went from 117 to 186 in that time span to the point of your pic.
To be honest, I am just not "feelen" that, young man. First, even if everything
could possibly be right (which in most cases it is not), gaining upwards to 20+ pounds of muscle (in an approximate one year) is a potential but is not often reached in the "natural" sector. With this in mind, lets say you gained less than 20 pounds of muscle (which is pretty safe assumption).
This would mean that the remaining (outside of other improvements or changes like tendons and what not) is fat tissue. 186 pounds (current wgt) -117 pounds (former wgt), is approximate 69 pounds gained in just over a year. And, I think we concluded that all this is not muscle.
A tad over a year is not that long, and dependent on where you started, getting 16/17 inch arms will not come over night. Over night (for some) IS IN FACT ----a ONE YEAR time span.
Which leads to my point: Your fat growth exceeded your body ability to put on muscle, and to be honest, it is obvious in the pic. This is not a mean statement, but giving an honest assessment and opinion.
It is going to be difficult to narrow down your problem, unless you provide more information about this passed year. Such as your diet perimeters, schedule of training, what training with, etc, etc (you get the point).
I do know one thing though. Focusing on.....your arms to make them grow, is an error for one wanting size.
Be more specific and be honest as well.
Best wishes
Chillen