Grey water indicator is yellow even tho drain is open

2008, 30' Classic Limited. Full timer in Florida. After emptying the grey water tank the indicator is green. Then after a couple of hours it suddenly turns yellow. No shower, no heavy use of water. This has been happening more and more of late. I do cook frequently but am diligent about not putting garbage or grease in the sink. My Micro Pulse is only two years old. I have never experienced an overflow.



What might anyone suggest?