Starting Over?

 I have not been on here forever.  I've been battling the red slime algae and now hair algae also for a couple of months.  I have a 40 gal. breeder with a 20 gal. sump/fuge with 175 MH and 46w actinics for about 4-5 years and this is the first time I have really had any serious problems.  I've tried scrubbing and cherry picking the rocks but the hair algae has now moved even onto the back wall.  My once pristine tank looks like crap.  I currently have about 60 lbs of live rock  and about 1 1/2 - 2" sand bottom.  The only thing in the tank now is a bubble tip anome with a maroon clown, a blue legged pistol shrimp and two small pieces of zenya. 
I am seriously thinking about taking everything out and cooking the live rock again to kill off everything and start over. I know my protien skimmer is at least 4 years old and hasn't seemed like it was doing very much for a while.  I haven't tested the water for at least 6 months but I was usually pretty good about doing 10% water changes about every 3-4 weeks.  I have tested my r/o water and it is showing about 24 ppm but that doesn't seem outrageous.
Anybody have any thoughts.  I have read tanks with sand bottoms just seem to crash after about 3 or 4 years and I am wondering if too many nutrients have gotten trapped in the sand and the live rock.
Mac