I posted something similar a few weeks ago.
I've got a 6, started slowing down dramatically after an update just over a month ago.
Charging port has started playing up too.
No chance I'm forking out stupid money for more of the same.
I'm thinking about going back to a Moto X or Galaxy S6...
I'm sure these software updates are designed to slow down the older models. I wouldn't be surprised.
I'm consider switching to Samsung to be honest, the S6 looks decent enough and I'd probably only have to pay $200 ish after selling my 6.
Maybe even switch to Motorola for nothing and be done...