DH has long said that he thinks DD is slightly deaf but I've always laughed it off as normal toddler behaviour. Recently though it feels like she's saying "What?" or "I can't hear you" a lot. I put the tv on for her this morning very early (so it was very quiet) and put the volume on low, but perfectly audible to me, and she said she couldn't hear it. She also quite often asks me to put the sound on when she's playing on the ipad when it's already on, though quite quiet. She also tugs at her ears a lot when we're swimming and they've been under water, not sure whether that's relevant or not.
Does this sound like something I should get checked out or just within the bounds of selective preschooler hearing? I did just quietly ask her if she wanted a party ring and she said "What?" 
Read on another thread about using olive oil so might try that tonight but wondering if we should investigate further and if so how - GP as first port of call, presumably?