I would say enjoy it. If things do start bleaching, there are things you can do to increase your nitrates. First, remove the macro algae. Feed your fish more often (at least twice a day), and more at each feeding, add more fish, feed the oyster feast more often, and remove any other nutrient scavenging device like the gfo.
Also I would suggest removing the carbon as it takes things we don't measure from the water which could also be responsible for bleaching. There is really no need for it. If you are running it for water clarity, consider a UV instead. It will make your water crystal clear.
Some people choose to dose things like stump remover etc to bring nutrients up but I wouldn't recommend anything like that unless you are very experienced and have years in the hobby. You may be asking for trouble.
You can also dial back your skimmer if it is removing a lot of skimmate...or put it on a timer running it 12 hrs on and 12 hrs off.
These are a few things you can try if you want your nutrients higher. Bottom line though is learn to read your corals and let them tell you want they want.
If your corals currently look good....then great. But if you want your nutrients higher, I would try some of these, one or two at a time. A lot of time, coral bleaching can be from a lack of trace elements, strontium, iodine, etc. I would make sure those things are in check via something like a Triton test before I started dosing stump remover.
If it were my tank, I would take the macro algae out and take the gfo/carbon off line. Then start feeding the fish 2x/day and the corals with oyster feast 2x/week. Do that for a month and check params. If they still aren't coming up, put a timer on your skimmer and run that for a month while keeping the first things going.
I'm pretty confident that will do it for you. I wished I had that problem. My nitrates run 10-20 and my PO4 about .30, but my corals grow like crazy, and the colors are insane, so that works for me.
I mean think about it, you are concerned about low nutrients, but you are running macro algae in your sump and gfo in a reactor.......all which are designed to.....wait for it.....remove nutrients.......good luck...report back your results