Using Coolant, Can't find a leak

[KDRacing]

I noticed i was a little low on coolant about two weeks ago so i added some and brought the tank up to the bottom of the max line, I didn't really think too much of it at first. A few days later it was back down, So i topped it off again this time looking for leaks after driving/sitting... Nothing, no wet spots no drips.. So i continued to drive it a little more keeping an eye on the coolant level, it goes about 3/4" below the seam in the tank and stays there no matter how much you drive it. It almost seems to me like the tank has a crack but I couldn't find anything wrong with the tnak as hard as i looked. I even went as far as unbolting the tank and laying it down to see if it's dripping from the top part of the tank somewhere... again nothing. I topped it off again today well see if it drops again. Anyone have an idea of where my coolant is going?

[KDRacing]

Still having this issue, can't figure it out.... Any suggestions