They don't need help. They need time Every minute they're in the shell they're doing something. Especially the last few hours. Those are critical to absorb blood and yolk. Which you've already learned. Chances of 14 chicks actually being shrink wrapped, when humidity was ok throughout hatch, are...
My first thought is you said you only waited 12 hours before "helping". Is that correct? Regardless of what day they pip I never assist until a full 24 hour post external pip.
What you're describing sounds like the eggs lost too much moisture. Seasonal changes in ambient humidity could be...