ACV Help! Apples got moldy. How do I avoid since fermentation weight fell to bottom??

I just started doing my DIY ACV. I got a fermentation weight and followed a recipe. The apples got soft and rose to the top with the fermentation weight dropping to the bottom. The apples then got moldy so the batch is not good. What did I do wrong and what should I do to avoid this again? Smaller jar? More apples? I want to make my own "Mother" so I know its organic and chemical free.