I was wondering if someone can take a look at these pictures and  determine if this is a leaky tank or if it could be a different issue?

This is what I saw when preparing to clean my truck for the 2016 season

I hired someone to run my trailer for the past year and a half.  I am unsure how long it took for this buildup to occur. I have the same issue on all 3 fryers, the left side of the fryer looks like this on all the fryers, the right side is clear. The fryers are MKE if that makes a difference

Thanks