SSD Drive issue

I bought 2 Samsung 990 4 tb drives, the read write speeds seem wrong (low) reseated the “c” drive (nearest to CPU) and it went up a little for a day, but next day I tested with magician and it was back down. Called Samsung tech support, they said they would do a RMA by email, never got it, said cache was bad. Now I don’t know what to do. Put in a second and cloned the first one, but it made a d and e drive out of it, thinking of an old program I used to use called partition magic, wonder if it’s still out there. System seems to run fine and fast but don’t know what to think. North of Boston.