Bananas showing up in late flower on an auto usually trace back to stress rather than bad genetics, though cheap seed makes it more likely. Light leaks do not matter for autos, so the usual culprits are heat spikes, root problems or heavy defoliation. I checked the list of stress triggers ranked by frequency on https://turboautoflowerseeds.com and root damage from transplanting topped it. Keep a close eye on the lower buds in the last two weeks and pluck anything suspicious.