Lost 3 stone now plateaued for months!!! How to kick start weight loss again?

[AquaAqua]

I lost 3 stone relatively consistently over 4 months. I've not really put any back on but have plateaued now since July time. I think I got happy and stopped trying as hard. But in reality I still have 1.5 - 2 stone to shift. I eat relatively healthily still (though will have treats and the will have a drink in the evening), run regularly etc but have stopped being really strict low carbing which was my main approach (though I didn't really subscribe to high fat - just lots of veg and low fat protein). I need to find some motivation to get back on it and wonder if it is worth really low carbing again to kick stat my system - I still don't really eat bread, pasta, potatoes etc - but not strict anymore. I'm not sure I could up running any more - I've run two half marathons and run 3 X 10k a week on average. What would you do to kick start the final furlong again?