see list at link.. refer to viruses ...:

https://extension.psu.edu/gerbera-diseases

since ll your stuff is potted on your balcony.. launch this pot into low earth orbit.. and be done with it..

buy a new one next spring...

to me.. it wouldnt really matter what the issue is.. i just wouldnt be interested in spending money.. in late fall on a basically disposable plant.. aka.. throwing good money after bad money.. or whatever that saying is...

and for a shiny penny.. i will tell you how i really feel about it ..

ken

Viruses Leaves may be mottled, have yellow spotting, dead flecks, line or ring spot patterns. Plants may be distorted or have flower color breaking.

Tobacco rattle, gerbera mosaic, impatiens necrotic spot, and cucumber mosaic viruses.

Maintain good insect and mite control.

Plant in pasteurized media.

Destroy infected plants

This is a mild case of fasciation. Fairly common in Gerberas. There are various causes but there is no need to destroy the plant. It'll be dead anyway as soon as you get cold weather.