'Goldfinger' is resistant to all races of Panama Disease, so it's highly unlikely it is that, and there would be other symptoms too.
To me it looks like Banana streak disease, in this case caused by Banana streak Goldfinger virus (BSGFV). There are a number of other streak virus species which affect other bananas. The challenge with managing these viruses is that they are integrated into the banana genome, and are expressed as a gene basically, so there is no way to rid the plants of them, only destroy the plants and start again with non-actively expressing material. As such to detect they are active a serological based assay (such as ELSIA) is needed as opposed to DNA based as the DNA based assays (such as PCR) will detect the integrated sequence regardless of if the plant is actively infected or not. I'm not sure where you can send samples for testing, Agdia which is good standard for testing in the US does not yet seem to offer services for Banana streak virus species. Perhaps you can contact the extension service at UF:
Florida Extension Plant Diagnostic Clinic | Tropical Research and Education Center, UF, IFAS
They tend to activate under stress conditions, but there remains a lot unknown about these viruses. Symptom expression can be highly variable from light streaking on the leaves and nothing else to severe bunch stunting and total yield loss. Occasionally symptoms may disappear and the plants can resume normal growth, but as far as know there is no surefire way to force that to happen.
I wouldn't be so quick to determine it has spread to your other plants just yet, the streaking to me looks different than the classic symptoms, and sometimes infected plants suffer no real damaging symptoms anyway.
Here are some of my photos of BSGFV symptoms on a 'Goldfinger' plant. The fruit never grew larger.
https://goo.gl/photos/oaaLtdnGPHft4jMo9