I'd beg to differ on ULNS needing a lower alk. I have run around 9.2-9.3 with nitrates and phosphates near zero (less than 1ppm nitrates and less than 0.01 phosphates).
Where are the bleaching coral located in your tank - bottom, mid, top? Seems you have measured par, what is the par level you are getting where the corals are located? What's your flow look like? Are you dosing? If so, what do your alk/calc swings per day look? One big dose or small doses through the day?