In July I put them back on my usual plain 5 grain mix, and they were flying like rockets.
Then, as usual, I stuffed it up.

I figured that if they were going so well on a light mix, by adding another 10 % of maize to increase the energy, well, they would have to be better.
Wrong.

They scoffed the extra maize for a couple of days, then started leaving it. And started flying a bit sluggish around the loft.
So, we are back on the usual light feed, it looks awful to someone who used to feed a big heavy feed,

Moral of the story. If it ain't broke, don't fix it.