[Can someone explain why I get these thin lines?]

It is happening while I work though as apposed to on the render? Also the adding a stroke or background doesn't help it.. Any suggestions? 

[Can someone explain why I get these thin lines?]

Thank you!

[Can someone explain why I get these thin lines?]

So I have recently just got affinity and so far it is great, I am having an issue though. I am using the isometric grid to create something but there is very thin white or black lines between the different shapes which I keep noticing, the shapes are right next to each other too so it isn't a gap. I am not sure if this is to do with my laptop or the software, does anyone know what this is? Sorry if it is obvious.