What's with KiCad telling me these pads need to be connected to ground, when they already are?

[j4cobgarby]

Attached is a close-up of the microcontroller on my PCB. Excuse the horrific routing, it's my first PCB.

I'm very confused as to why those thin white lines are there. It seems like they're telling me that my ground pads should be connected to the other ones, but surely they already are, through the ground planes?

 

[j4cobgarby]

Nevermind. I've worked this issue out, turns out the ground planes weren't connected.