isn't that film developer as well? Also, when using paper developer the prints need to develop for 90 secs.
what was the filter grade?
Prints look better wet than dry, and you need to figure out the dry down times and apply. RC paper has less dry down than fiber, but it can look quite different when dry.
What is happening is just the learning curve , and we always end up with more prints going into the learning bin before they are ready for the wall.
(learning bin=trash can)