Performance Drop With Multiple Webquerys

I have built a fairly complex app in excel which takes 50 webqueries and makes a table out of specific data. It generally takes ~34 seconds to run through the webqueries, and when its done, it starts all over and runs the 50 queries again on 30 second delays. My problem is that for about 5-10 of these cycles, everything works fine, but after that, the time per set of queries starts going up...in the range of 2:00 or more for the same 50 webqueries that originally took ~34 seconds.

Without posting each of the userforms and modules, is there a general way to clear out the memory or see whats bogging down the process or anything between sets of queries to maintain performance? the webquery itself is a

With ActiveSheet.QueryTables.Add(Connection:= "string" & variable

statement that gets called each of the 50 times. The only thing I can think of is that somehow variables or some other procedure isnt clearing after each of the sets of 50 queries runs. Is there any way to check that or make sure it is cleared before it begins the 50 query set again? I noticed this mostly by watching my "physical memory avaliable" drop a small amount each time the set ran, and I had to quit excel before it would return to its original amount.