I'll pretty much echo what everyone else said. Definitely cut back a bit on the lighting - also, what kind of lights? 14 hours/day for 6 months - they may also be at the end of their life.
The stock is about six fish (lion fish, trigger, paddle fins) and some live rock
If all 6 fish are the same relative size as triggers, lions, etc. ,then I'm guessing your are significantly overstocked for a 72g. I'm going to take a wild guess, and assume you have about 24-25 inches
of fish in your tank - which is about the maximum stocking limit for a 120g.
What are your nitrate & phosphate levels?
You mention "some" live rock - how much? If not a lot, what type of filtration are you using?
Are you using and RO
filter for your water? Water changes are great - as long as the water your using to replace the changed water is nutrient and contaminant-free.
Algae needs 2 things to thrive - food & light. You can cut back on the lighting, but most algaes will thrive even with minimal light. The trick is in nutrient (food) removal - nitrates and phosphates being the big algae 'boosters'.