Nexus 6P Now Showing "Charging Slowly" After Turning Off Boost Charger

Hi all,

Firstly, I'm new here and I apologise if I am asking a dumb question. I've searched the threads here and followed how to get rid of the ads on the second charging screen that S Photo Editor was implanting via its dodgy adware.

However, now I've found that since turning off the Boost Charger, my phone says "Charging Slowly" when I plug it in to charge. Is this a legit issue or am I being naive and still have some bloatware/adware on my phone?

Thanks in advance for your help,
Amaliah