>>>>fluvial 304 canister with no media in it to lower nitrates
I'd bet this is only adding fuel to the fire.
>>>>I do weekly water changes 5% per week with RO water form the lfs.
I also agree with the others that 5% is not enough and I'd be willing to bet the farm that the RO your getting from your LFS is not good. I did the same thing for a long time and the TDS was 40!!!
Ask them to check their TDS and watch what happens. This should help a lot.
Chris