Hi Brubon,
Welcome to the Heartland Owners Forum. There's lots of useful information here along with a great bunch of friendly and helpful people.
I think a yellow flame might be due to too little air in the mixture. Lift the cooktop and see if there's anything amiss.
Also, as a general rule with all your propane devices, it's always a good idea to check the propane tanks to make sure you're not running out.