Yeah they do look a bit short. I struggled a lot with heights in these drawings, but it's alright.
Shadz is meant to be about 5'11/6'0, Levi is 5'9, Kumo is 5'7, Miri and Kyer are around 5'5, 5'4 and Lulu is the shortest at 5'2/5'1 (around abouts) I'll probably adjust them or such, but Levi didn't turn out so bad imo.
I just fail at portraying heights :p