You need to take a bit more time and study all of your options in the "Behind The Scenes Menu" found on your Account. Then make some informed decisions regarding how you want to sell your work and the pricing structure. That way you do not get blindsided by something like this.
I am guessing there are some pricing issues going on.. I can't believe that would be a Designer prints price. Can you share the links to what you sold? Putting the links from the announcement page will suffice
Looking at your markups, they are nearly identical from the smallest size to the largest. That's going to present a problem if you participate in the Designer Prints program and get orders with a heavy discount. Your markups should increase as size does.
first, raise your prices
second get an avatar so you can be seen in the search
third, this sounds like a designer print sale and you are still charging too little.
retail price is their and your mark up together. i think both the site and you take a hit when they discount it. but it could be a bug of some kind. or your prices are messed up for those images, double check them. did you offer a discount code to someone? maybe they used it and went to DP (it would day if it was a designer prints image).