Suddenly unable to capture accurate red reproduction.

I would suggest you have a look at two things, one your white balance, instead of using auto, use a grey card and set your camera's white balance in custom.

 

This is very good advice! Auto white balance will only work if there is something pure white in the scene! In your case, where you’re shooting these beautiful flowers, there may not be anything pure white in the scene. Using a gray card and setting white balance from it solves that problem.

 

"Auto white balance will only work if there is something pure white in the scene!"
you know what, its obvious when its said but never even thought about that!!
yep i use the custom setting with the grey card in camera too, i also take an image of a mickey mouse colour checker with greys and whites too, yep i know but its for my own use, i'll get a real one if i need to send out or print etc