I have balloon mollys and mine are about to drop fry any day now. It definitely feels like a long time. I hear if you keep the temp higher, like 78 - 80 degrees, it helps them give birth faster but warmer waters irritate fish. If you have seen fry before than chances are they are still pregnant, and if you have a male in the tank they will always be pregnant.
However, I believe you are feeding them too much. Once a day is enough, from what they tell me. My balloon mollys are aggressive fish so they need to be fed well. But I was feeding them too much to the point the males where getting a belly, and me thinking they were caring fry, when I finally realized they were male and just overweight. They can die as a result.
Also, if you are feeding 2x a day, your nitrates should be higher than 5. You don't want it high, but feeding them 2x a day would definitely raise those nitrates. That's because the more they eat, the more they poop, and the more they poop the higher the nitrates go. Because I was feeding them 2x a day too, my nitrates were going up and I had to do a 20 percent water change 2x a week sometimes. Also, ph 8.4 is very high. It needs to be b/w 7.0 - 7.8, but definitely under 8. You might need ph down. When ph is either too high or too low, it effects their scales and are susceptible to disease. I had guppies in particular swim and eat perfectly normally and then die the next day. Also, did you cycle your tank?