Id hold off on the ICP test until you can start ruling out the common variables/issues that prevent proper troubleshooting, get more accurate test kits, get a more accurate way to determine salinity, temperature and other parameters before dropping the scratch on ICP.
If you posted your params and said they were determined with accurate, proven methods/kits, Id say bump up nitrate a bit, stop dosing alk until it falls to ~8, get PO4 to a reasonable level and maintain that for a week or two, if everything thing still looks cranky, thats the point where Id recommend ICP.
just my .02
Right now, for all we know your salinity is 1.031 and your temp is in the mid 80s
eliminate the common variables first