[Orient Express]

You want to keep each individual lighting leg fuse at 10 amps, they will be fine as these ballasts only draw 8 amps at startup. The main "doomsday" lighting fuse is 20 amps, so you are already covered for a catastrophic failure.

So leave your fuses alone. Remember, you want to have the smallest amperage fuse that will carry support normal operation of that circuit. Typically the fuse is sized at 120% of the normal highest current draw of that circuit.