As an artist myself I am going to critique you.
The pieces you have put out are well done. I know its digital cause I do digital also. I come to noticed that the pictures match up to the T of the pictures given to you for references.
As a digital tablet users are you tracing the photo then using the smear tool? I see you are adding in your own to make the eyes deeper and lighting on the fish, but like I said it doe seem like you are tracing all these pictures.
I used to trace to for practice. I think most artist do, but you will soon move away from it and be able to do it all on your own with time ^_^
Keep up the fun work.