I just got this thing a little while ago and did a Blackmagic speed test for the first time. I have a Toshiba SSD My write speeds seem RIDICULOUSLY slow. It maxes out at 220 mb/s for an instant and then plummets to around 150-170 where it likes to stay. My read speeds are frequently in the high 300's to mid 400s so those seem okay. It's a 13 inch with 8 GB RAM model. Are my speeds unusually slow?