Before you plugged your heaters into your RKL, were they heating the water above 76.5 degrees? If the PC4 light is on, that means that the circuit is on. Whether or not it's heating depends on the heater.
It sounds like you need to dial up the heater a few notches. I don't recommend dialing it ALL the way up, just one or two clicks above where you need it to be. The RKL is not 100% failsafe, just better than thermostats on the heaters.
Also, make sure that the "default" is set as "OFF". You don't want the heaters to automatically go on if the RKL temp probe fails.
Sorry, don't know about the actinics in storm mode. I'm thinking no, since you would be effectively using storm mode to override a timer. The only thing I know of that overrides timers is the standby mode.