RAH, I do think those smaller WM are offspring of the originals. WM grow slower than BG and RES ... comparable to GSF. Once they attain around 4", males can grow up to about .16 lbs annually in your climate. ~6" inches at 1.5 years is or is near the upper limit. Males do grow faster than females. With only an initial stocking of 10, those initial probably grew at their full potential the first year. If they grew at near maximum rates of growth ... and were stocked at 2" ... there could be some males around 7.5" in length presently.

With regard to the minimum length or age to spawn. I recall a Texas study where the research found that the length (of an altogether different species) depended in part on age. Shorter fish became mature at greater ages and vice-versa. But the pond has been stocked only for a couple of years and it seems likely that the fish that you referred to is either from last year's or the initial year's YOY crops. I lean towards last year's crop but if the they reproduced significantly in the initial year ... it is possible that the fish is approaching 2 years.

Thought I would mention a couple of things about balance. Without any predators other than the WM themselves, they probably have reproduced more abundantly than could support moderate/fast growth. Wanted to ask how the FHM are now doing. If they have been extirpated, good chance growth is now going to be slow going forward. The smaller WM being survivors of predation by their WM parents have probably reached a length that can only be consumed with difficulty or not at all. Bill Cody introduced a practice to the forum of adding a single LMB to a small pond to provide predation to a less fecund species. Being a 1/4 acre pond, it may be a good candidate and you probably could spare one from your LMB pond if you chose to do it. FWIW, I would want the LMB to be 4 to 6 times the length of that strong year class of forage. At 2.5" Forage ... I would want an LMB of 10" minimum length. Though it may not provide sufficient predation for the WM grow at full potential ... i would think it would have a positive influence on growth and condition of the WM.

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