Is the helium good.
What size are you inflating the latex rounds, are they helium quality?
The foils, are they big enough to float, some foils are air filled only.
Are the foils good quality, are you using a rubber or metal to inflate,
on metal you may have a slight burr that is damaging the balloons when inflating.
Are you sealing the balloons correctly, many things can be causing the problems.
I'd better say I do not do décor, just twist.