i got my oscer 6 months ago at 3 inch it is now about 5 inch should it br bigger now or is this the normal size for this age it is on its own as it bulled the other oscer so i seprated them it is in a 70g tank

I would expect it to grow slightly quicker. However, some Oscars don't grow as fast. What do you feed your fish? Do you carry out regular water maintenance?

i feed them color flakes, shrimp ,pellit food and some times a bit of meat like beef heart and yes i do a 25% water change every week and a ph test every week

at normal feeding rate coupled with regular water
change, your oscar should grow 1" per month or 35%
of the total food consumed in 6 months (in weight).
however, there are some instances that some species
do not grows that fast, either by genetic or because
of some restrictions: water not good or controlled
feedings.