weird bug

my boosters (double fish, etc...) get black, or the place where you see them is. It seems they can be used though, if you know which place to click on as you only see black little circles. It has happened several times, and goes away -so far after a while. Today, when it went back to normal, I noticed my black balls have gone from 18 to 9, though I only used one. Since the disappearance of the quests, I only use them with a lot of caution and know how many are left. I'm quite upset. Can something be done? Thank you.