Tires Excessive Front Tire Wear

My buddy & I operate a small mowing service in our hometown (population 800) - we have 12 lawns we care for weekly. Two of the mowers we use are 2008 42" Craftsman & both run fantastic! However, one of them wears out both front tires EVERY YEAR while the other is still running on the originals and they look new!

Can anyone provide some insight? These tires aren't getting any cheaper!!!

Thanks in advance for any help anyone can give.

DB