Is this normal for an ssd?

[WantYouGone]

Hi guys I'm new here, I don't know much about ssd but a couple weeks ago I noticed that whenever I'm copying a file the maximum speed it reaches is around 30 mb/s sometimes even going down to 5 mb/s, this wasn't happening when I first got it 2 months ago. Is there a way to fix this? I've got a 2.5 inch WD Green 120Gb, also I checked with WD software and all the drives are up to date. I have around 60 gb free so its only half way of its full capacity. These are results diskmark gave me.

[Guest]

It's common for low-end ssd to have those write speeds, don't know in that specific case, but mine has 300MB/s in read and 90 in write and is a very low end one