It seems to me that your just guessing at everything. I am not trying to be rude but I want to get to the point. If your having problems with animals surviving then start with your water. Test the R/o water for ammo, nitrites, nitrates, phos, and silicates. That will give you a starting point because if your using water that is not correct then your just defeating the purpose of doing water changes. Then test all your water parameters for the aquarium water then you will get an idea of whats going on in the tank and this will help with a course of action. Explain your setup to us here along with the parameters so people on this board can give you more specific help or recommendations. also maybe get rid of the wet/dry if you have enough live rock and a good skimmer. There are numerous reasons why inverts die and some of them are salinity levels, ammo, nitrites, nitrates, copper, and of course acclimation. hope this helps and take care.