Growing Time Suddenly Decreases in Farm

Hi. yesterday in my farm, when my mushrooms are filled %100, they'll suddenly decreases around %40, and again they grow up, decrease again, and again. At least (i think 4th time), they are not dropped and finally i was collect them. Okay. But this problem is not solved, it happens again today and i don't understand. They have fertilizer, water, and warm enough but idk whats wrong. Maybe this is bug, or something i missed. Can anyone help?

 

it happened again... when its %100 and glowing, after few minutes its suddenly dropped around %80 and glowing again like %100 growing rate, why is this happened?