Not growth, to me it does look like maybe a fungus growing? If it were me I'd put a dab of anti fungal cream on it a few days if it doesn't come off with a toothbrush. Let's See what some other more experienced keepers say. @Markw84 @Yvonne G and @ZEROPILOT knows a lot about shell rot.Does it look like growth or rot?
So the white did not go away but the lines became very thin and looks more like growth nowNot growth, to me it does look like maybe a fungus growing? If it were me I'd put a dab of anti fungal cream on it a few days if it doesn't come off with a toothbrush. Let's See what some other more experienced keepers say. @Markw84 @Yvonne G and @ZEROPILOT knows a lot about shell rot.