I have a pair of discus in my 55g planted tank my turquoise seems to be abusing my sunrise discus he hides a lot should I get more discus and if so how many?
Unless you get a proven mated pair, keeping 2, 3, or 4 discus is not a good idea - generally results in unwelcome, often serious, pecking order/aggression issues, like you seem to have.
You should get 3 more (or 4 max.) discus to dissipate the aggression, but only if you have no other tankmates in that 55 gal., or just a few - otherwise you may need to reduce the number of tankmates in order to maintain a reasonable bio-load.
5 is the normally recommended minimum. Most folks say a 55 is good for 5 or 6. Of course 6 is a lot more of a bio load than 5, so you would really have to be diligent about keeping up with the water quality.
A lot of people use a sump filter, which increases the water volume.