How does the turf scrubber work for you? Are you seeing a lot of algae growth in the scrubber and are you then harvesting that algae with any frequency?
You may want to "find" that star fish as its demise might be part of that rise in nitrates. I agree with SilentKnight you may want to consider some form of bacterial additive and get into a regular schedule with filter cleaning. I still occasional use Bactiv on my 20+ year old system and there are other bacteria additives in the market that are good.
Also, I see you have a fairly deep sand bed. Many people like and advocate for that type of system however, given past neglect, you may want to "vacuum" a section of the bed with each water change. Maybe 20% of the sand with each water change. (just a guess but do it small stages).
Before I began with corals 5 years ago, and just had a fish and live rock tank, my nitrates also ran very high. It never seemed to bother my fish, but algae grew like crazy. Keeping up the water changes will help (they certainly helped me)! It will just take more time, be patient. You may find in the future that more changes to your system are needed depending on what you are wanting to achieve.
You should come to our monthly meeting, its mostly experienced reef keepers socializing and having fun. Usually there is an educational topic, but meeting the group you will find they are happy to help you. You'll also see some really nice reefs and learn how the host of the month is running their system.