The Baggies slipped to a 2-0 defeat at the KC Stadium on Saturday to leave them precariously perched just three points above the drop zone.
A familiar face came back to haunt them in East Yorkshire, with Shane Long winning a penalty, finding the target and hitting the post.
Mel feels the Irish frontman, who West Brom agreed to offload in January, went to ground a little easily in earning a first-half spot-kick, but the Spaniard is refusing to dwell on decisions which cannot be altered.
Asked if he felt aggrieved, Mel said: "It is normal. It is the first penalty in eight matches and I think today it was a bad decision by the referee.
"In the second half, with a same situation in the other box, the referee didn't whistle. But we continue because in the Premier League every week the table will change.
"Shane Long is a good professional, a good attacker. Now he is a player for Hull City and for us it is the same, we need to play well, hard work, it is the same for all the players.
"Shane Long is a professional and only wants the best for his team. It is normal."
West Brom's next outing will see them welcome fellow strugglers Cardiff City to The Hawthorns and Mel admits that contest has taken on added importance.
He added: "Always the coach, in my head, I am thinking to win. Today it wasn't possible but Fulham lost, Palace lost, Cardiff lost, Sunderland lost. The next game is a big game for us."
The Baggies may, however, be without the services of a number of key men next weekend, with Gareth McAuley and Victor Anichebe picking up knocks against Hull.
Mel said: "That's a problem for us. (Jonas) Olsson is suspended, McAuley is injured, Billy Jones too and Anichebe is possibly injured too. It's a problem because the next match is a big, big match for us.
"McAuley has got a very swollen ankle and Anichebe has a muscular problem."