Nowdays ,my favourite blend is 3000°K 80Ra and 3000°K 90Ra ,at a device ratio of 1: 2 ,respectively.
( I'm using Citizen CLU048 1212 for this blend of white COBs. )
I've some plants at 12/12 from seed and the COBs are driven @ 700mA .
I've to say that it is the best blend I've tried ,so...