Help with breakage in the middle

So, I have thin curly 3c hair, it's fairly long, past my shoulders and I really like it that way, but it keeps breaking in the middle to the point where there's a notably length difference with the other sections, there could be a number of reasons, I have chronic iron deficiency and use box dye sometimes, but my main doubt right now is, should I cut the rest to match the middle part and let it grow evenly? or should I focus on growing the middle part? my routine is pretty normal, I wash it 1\~2 times a week, use the fine&fragile brush and leave in, recommendations of habits and products would be more than welcome! Thanks!