Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Cold tolerant FA species?

Hello PB gang. I had a new occurrence at our pond this spring. Normally, any living FA mats we see in the fall are killed with frost/freezing and ice formation. So in the spring we start with clean edges on the pond. This past fall, I noticed the FA mats didn't seem to die with the fall freeze, and could actually see FA on the surface and frozen in the ice this year, which was a new thing. Then at ice off, those same FA mats didn't sink and are (mostly) greening back up. So instead of a clean edge to start the spring, we already have 30% edge coverage or more. Very disappointing way to start the spring. We have a very old (eutrophic) pond, and always fight FA. However, we've learned to get pond dye in at ice off, and keep adding every month or so, to cut down light penetration in the shallow edges. This helps to a degree. We then put down copper granules around the edges right away, to hit the FA mats that appear on the bottom, before they get growing and any surface mats form. Next, we use liquid cutrine plus to spray any surface mats that do appear, and repeat this about monthly. With this combo, we can keep our edges fairly clean (not perfect, but not much FA). After reading a bit and working the PB forum archives/threads, I am worried we have developed a copper resistance and/or cold resistant strain of FA. Anyone with experience with something similar?
I am hope Bill Cody will see this post and chime in. I almost just direct messaged him, but posted my question instead, so any possible solutions could be shared with everyone.

Unrelated side note, saw 7 wood ducks on the pond this morning! I have our duck boxes re-set and ready for takers. I might try and stream from our duck box with the camera again this year.