Down here RES in their 2nd Summer can spawn. How old would Michigan RES be at 3 to 4"? Possibly in their 2nd or 3rd Summer? So it looks like an RES spawn may have happened. There are so many, that the growth is slow for that cohort. I wouldn't think that would be a problem for SMB that are big enough to eat them. As the SMB thin them, their condition should improve and they should grow and still be food for the growing SMB. Maybe all this is good? Unless you do have BG and lets hope that didn't happen.

Its been a while but if IIRC, I once read a report by Michigan's DOW on RES. Seems like their recipe for producing fingerlings was only 5 or 6 pairs to the acre and the production was in the neighborhood of ... wait ... let me find it. Here is exactly what they report on producing fingerlings.

Quote
From 4 to 6 pairs of adults per surface acre of rearing pond
has produced similar fingerling harvests as twice
as many adults, therefore the lower density has
been preferred. A rather high broodstock
mortality rate has occurred in some cases, so fish
handling has been kept to a minimum. Harvest
of fingerlings has occurred in September
through November at harvest rates of about
25,000 to 30,000 fingerlings per acre; however,
annual production has been variable. Depending
on the growing season and contamination of
ponds by other fish species, the harvested redear
sunfish fingerlings have ranged in size from 1.0
to 2.5 inches in total length.

Hopefully you don't have BG and if not it looks good for the predators when you add them?

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