A friend in Malaysia asked for my help in figuring out what is causing this. He is adamant that he only fertilized infrequently with Phostrogen (a MiracleGro-like product made by Bayer) and gave them Epsom Salts early this year. I was sure it was something superficial until I noticed that the discoloration follows the leaf segments on the Gunnera, so it must travel in the phloem.
