Opencv how to make edges more visible

Can you give me some advices how to make white balance, i am a beginner in image processing also i would like to know if dilated circles like that would be detected with HughCircles because the main task is to calculate them based on shape and color.

If not i will just simply switch to HSV masking and ignore the white gummies

For the rest worms/bears i wanted to add rotatedRectangles and try to detect them with ratio of sides because worms have much lower ratio