Here's my girl Dragonfly. She's not a marble, but she did great from when I got her at walmart. She was sitting in that cup for 2 weeks. My walmart doesn't feed their bettas or change the water. The person in charge of the fish is stupid, yet they "know everything there is to having a betta". Sure ...
She actually recently survived a gill infection. Her gills got swollen and her chin turned white. She was like that for a month and I thought that she was going to die. After a month [wasn't thinking straight for THAT long ...] I gave her an epsom salt bath. She got completely better within 3 days. Her left gill juts out a little now [scar tissue?], but she's as happy and healthy as ever. :)
At the store
2 weeks later [brought her home]
2 weeks after that [home sweet home]
Now [fin rot finally gone and her dorsal grew back]
Also, here's my blue marble HM, Daemon.
Brought him home
2 weeks later
Another 2 weeks later
6 weeks of owning him
2 months of owning him
He stayed looking like that for 4 months until his death. Unfortunately, there was a pipe break in the city. I didn't hear about it or the boil rule, and I did a water change. Only him and my female betta died. My other fish got extremely sick, but lived. SIP Daemon and Mystic. <3