Why all of a sudden and out from the deep blue they get all green?

Dyckias do not perish nor succumb from blooming and blooming is a very energy consumer  work. 

when the plant is old enough to bloom it must search for the necessary and most needed energy

in order to bloom.

The cultivar yellow glow has less chloroplasts the the type for and  if it is living in an area where the light is not as  plenty as around the equatorial zone..so the only way to produce flowers is by making more chloroplasts in order to absorb the more it can from the migger light it gets.

that is why these yellow plants get greenish just out from the blue without no apparent reason..

Also this is why you has not seeing them blooming so frequently.

But believe they bloom and by the plenty.

So only adult to semi-adult plants get green so out from the nothing.

Remember, dyckias are all sun adorers and they live almost forever....

you do not must to get rid of the dead body as one must do with most agaves and all other bromeliads.

Dyckias are just perfect!