Two of them ('Cocky' & 'Birthday Suit') literally come from the Stuart Crichton sessions who has contributed to the actual album ('Let 'Em Talk' & 'Learn To Let Go'). They all were written at the same time along with some other titles that did not make the final cut and registered back in 2016 but since we know that 'Cocky' was already recorded in 2015, it is not hard to assume that the rest were at least composed and demoed that same year too...
It's also not hard to think that in two years time, the direction and soundscape of the record might have changed so we ended up with much more 'mature' sounding music on Rainbow.
