yes your units are to close and it does have an affect on the. I also agree with you second contractor that moving the unit apart isnt going to resolve you real problem
at best it will help the units effiency but you from what you have said have other concerns going on there
make sure the systems are sized correctly and the ductwork is also sized properly this can also cause the units to not operate properly and run you bill up
before moving them and the expense of it find out the real problem fix it and then move the units