You're off to a great start. Your images are generally reasonably focused and exposed.
I have the same lens. You can take some awesome pics with it.
Your first few pics could benefit from tighter framing / cropping. Frag racks aren't that interesting and tend to distract from the subject. Notice how much more interesting the single LPS (Acan?) above the Eagle Eyes(?) is compared to the zoas on plugs on frag rack shots. And even how much more interesting the tighter green paly (?) shot is than that. For me, the most interesting macro shots tend to come from showing pieces / parts of a subject compared to the whole frag and its surroundings.
With stationary corals and a tripod, you can get away with slower shutter speeds (upwards of a second or two even) which can allow one to get greater depth of field (by stopping down / increasing fstop number) or to use a lower ISO (less noise / grain, not that your pics are noisy).
The closeup of the mushroom coral(?), the first pic that showed up in your second post, is interesting to me. Color. Texture. Variations in lighting.