Steve Bruce's side took the lead in the third minute when James Husband got to the byline and Ashley Fletcher headed in his superb cross.
The hosts, who have the best home record in League One, responded well and equalised 21 minutes later through Mullin's stunning volleyed effort from just inside the box.
Oliver Casey nearly restored the visitors' lead shortly before half time, only for Mark Howard to make an excellent stop from close range.
Blackpool, who had the fifth-best away record in the division, conceded a penalty when Oliver Casey handled in the box, before Stephen Fletcher dispatched the resulting spot-kick three minutes from time.
Phil Parkinson's team secured a 2-1 victory at Stok Cae Ras to stay within two points of second-placed Wycombe Wanderers and three adrift of table-toppers Birmingham City.