So my cycle seems to have stalled at high nitrates. Help please? :D

[Xyres]

It has been about 3-4 months since I have started my tank. It is a 55g with canister filter which I will be upgrading within a year. I have two cleaner shrimp, two clownfish, and emerald crab and some hermit crabs as well as 50-60 pounds of live rock in my tank at the moment.

Now that we have some background on my tank here is my issue. My Nitrates will NOT go down no matter what I do. I clean my filter, run a protien skimmer, do water changes and monitor food intake, have excellent water flow as well as use RO/DI water. What would be the reason for my nitrates still being around 25-40? It is really annoying as I have been doing everything I can to keep it down.

Here is what my water was at today:
Nitrates: 30
Ammonia: 0.1
Nitrite: 0.1
PH: 8.2

Any help would be great and I will answer as many questions as I can to help figure this out.