Pond Boss Forums INTRO Questions & Observations What has happened to our bluegill?

Hi Guys, it has been a while since I posted but have another question but will give you the play by play to get you up to speed. My family purchased a home on a 20 acre lake (manmade) with very clear water and a sand bottom. The builder stocked bluegill, minnows, perch, and rainbow trout. It is in central Wisconsin and has 20 foot max depth with about 8 to 10 foot average. The bluegill,perch, and minnows were doing well for about three years and then the perch disappeared. For 6 years I had been putting in 14 inch or larger keeper largemouth in there 150 in total over those years and about 50 keeper smallmouth. One of the other homeowners told me he and a buddy had put some black crappie in there and I told him to stop that immediately after about 15 were transplanted. The bluegill population seemed unaffected and the bass fishing was awesome and this year, the bluegill have almost disappeared. I have a kayak and have gone out in the deep water where the bluegill would follow me around and they are not around. The bluegill used to be something the swimmers would complain about as there were so many and they would nip at your toes. Schools of 5 to 20 bass circle the lake and come as close as 1 few feet from shore to feed now. As I said, the population was great last year and now seems in serious trouble. There is minimal vegetation and they do treat the lake for algae and to keep the weeds down. The homeowners are not going to spend the money to shock it and find out what is really up. I know that we cannot determine anything for certain without shocking the lake but would appreciate your opinions. I just cannot imagine that since last year the bass has decimated the entire forage base. Thanks for your thoughts!