Params look stable, but there is always a reason to do water changes, are the scarlet and brittle not in this tank?
Do a H2O change and you should be doing better. Plan on those at least every 2-3 weeks max!!
I remember Hermin my first Octopus, after I found this site, took my water to my LFS and the nitrate was off the charts!! Deadly to fish, but Hermin had existed in my old tank for 4 months at that point!
I did weekly water changes to bring it down. 40 is not bad!! Good idea on Fish Supply, if you want I could email jim and beg him for one more!!!!!