With plenty to eat ... I would expect 2.5" Northern strain LMB to be ~9" on average now ... if stocked the middle of December. If you still have plenty of minnows, then my guess is they are growing at satiation.

If Tiger fingerlings, I would expect them to be just under 10" by now. You should have examples greater than 14" by October.

Is your water difficult to see into? If not, you should be able to observe LMB swimming about along the pond perimeter. You may try a small minnow-like lure or hand feed near the shore to see if LMB are attracted to the commotion.

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers