Ctenanthe help!!

She's dying and i don't know what to do.

I repotted her about 2 weeks ago because she looked sad and I thought there might be something wrong with the roots. They looked better than they do now. Some bits are clearly much and rotten but even if I cut those bits off I don't know what to do next.

Under a grow light for 14 hours a day.
Watered usually when the top soil starts to get dry, though I absolutely drowned her last night as the soil was dry and I thought she was drooping due to thirst. When she didn't look any better this morning I decided to investigate and found this