First I thought the light film in between LCD and digitizer then when you said it's acting up, now maybe the whole LCD assembly need to be changed. But it's a fairly expensive unit, I would get pro help.
Can you try to wash it with 90% or higher alcohol and rins it and then dry again with fairly mid high air. After that keep in warm area oven maybe around 100 degree. On top a heat resistant surface . I would use paper towel but keep eye on it. Although it will not catch on fire but still careful. I do lots of water damage phone repair , I use this method but also ultra sonic machin. Hope it help. If any thing I would not worry just contact apple they should take care of it