can't get past day 5

[BlackAndRedLipstick]

so i've had my breeding pair of golden melons for about 3 months(ish). After about 6 weeks they started to lay eggs. first batch of eggs they just ate them( i expect as much i had to do some major filter work that day and i know i stressed them out a bit). second time they got the eggs to hatch but then ate them again. and now ive got them laying eggs every 6 days on the nose but every time they spawn and the eggs hatch roughly on the 5th day the fry will not leave the cone. At first i thought maybe the batch was still born or that something wasn't right. I keep them at 6.8ph, temp 84, ammonia 0, nitrite 0, nitrate 20. As weird as it is the first day they ever laid eggs it was a day where i had no RO water so i used 100% tap and so since then i use only tap and go a 30% water change every 2 days in a 30 gallon tank. I feed them a beef heart recipe and pellets. Any ideas what it could be or what i should maybe change? should i maybe try taking out the fry and raising them without the parents?

[RogueDiscus]

roughly on the 5th day the fry will not leave the cone

Hi Nick,
Do the fry disappear (eaten), of fall off and die,...? I'm wondering what you mean here. I'm not a water expert, but also wondering, what are your tap water parameters?