Five bucks says you don't understand the system yet. If you have a gun with a mod on it, or armor, you're not seeing its "true" power level. Say its sitting at 268. That gun is actually a 263 in terms of your "true" power level. Infuse a 265 into it and it will jump to 270. Using this information I bet you've deleted blues that would have raised your true power level, thus increasing the power on future drops.