RH has been high after the switch. What can I do t...

There's a couple of things that you can do: the first is to increase the exhaust and the second is to try to increase both lights on and off temperatures, as temperatures rises the rH will drop drastically. Actually low lights out temperature is the main reason for high humidity during flower lights out, so if you can heat your grow space during both lights on and off it will really help and since you have your lights on temperatures at 19°C (66°F) there's some room for improvement. Good luck