Al I am fairly sure you have a catch problem not a LMB survival/growth problem. If you have good water quality , lots of forage fish and some LMB of different sizes ( under 4 inches , 8-12 inches and 14 inches and up)you should be in good shape. LMB feeding slows during cool water periods so fishing does also. In warm mths small LMB stomachs empty quickly due to the high metabolism and small size of food items. Do you see different sizes of BG ( 1-2 , 3-5 and 5+ inches)?