No not so much although of course there are maximum and minimum numbers for elements and nutrients. The numbers you quoted above are almost my parameters but I run alk at 7.8 to 8.2. There were some studies that showed you might get faster coral growth with higher alk but you had to have higher levels of nitrates and phosphate to supply the growth. Keep in mind NSW alk is like 7 and there is endless amounts of phytoplankton in the water for corals to consume. I try to mimic this by adding phytoplankton daily. In a closed system 7.3 is borderline low because given the test kit error rate you might be at 7 or lower and that leaves no wiggle room for problems.
