All symptoms of nutrient deficiency, been there many times, before to realize that 00 nutrients is only reason for TN of my corals. I prefer to have some algae and cyano here and there but my corals to be happy and growing. My advice is to stop GFO and start feeding more, it is good idea to dose some aminos or coral food if you have in hand, and never allow nitrates to go under 1 ppm and phosphates under .03ppm .