My pacman frog is turning white around his face mostly!

He lives in a 20 gallon tank
Humidity is 65-78 but most of the time its at 70
temperature 70-75
eats every-other day about 4 crickets and they are dusted on Wednesdays or Thursdays it depends on the week.
He has a large water dish
PLEASE HELP

Name: 20170806_193951.jpg Views: 288 Size: 3.14 MBName: 20170806_194018.jpg Views: 281 Size: 2.91 MBName: 20170806_194029.jpg Views: 284 Size: 2.89 MB