Why is my phone taking 3 hours to charge?

[AC Question]

A few days ago I accidently left my phone charging overnight. 12am to 7am. After that day on, 3 days till now, my phone takes so long to charge. Before that, it only takes about 1 and a half hour to 2 hours to fully charge. Now it takes about 3+ hours to fully charge.

I'm using my original charger and turn iff my phone while charging. Is it my phone or the battery the problem?