Morty, my drop in levels could be from reducing muck, but I think it is much more likely that as a water table or ground water pond, when we hit several weeks of dry weather and the grass starts turning brown under the bases of trees, that the water table goes down. So does my pond. I see where large trees have their roots that the grass is looking bad or dying. I think they are really sucking water out of the surface because the water table has dropped. They probably are pulling lots of water out of my pond too since I have mature oaks and maples on the west side of my pond with extensive roots. That cluster of trees by your pond probably also enjoy getting water from your pond as their deep water supply drops.
I wouldn't cut the trees down. I know they take water but they also are beautiful and I love that our kids can fish in the shade. The downside is lots of oak or maple leaves in the fall. I would not try to burn the leaves off a living tree. I would just let them fall. If you are really dedicated you can make what is dubbed a 'prickly rope' on this forum. IT is a long section of rope with various sections of swim noodles on it to help it float and some person with some ingenuity put a couple hundred zip ties on the rope with ends left long to snag the leaves as they pull the rope in a big arc towards shore.
I'm sure if we all put our heads together we can come up with a slightly more effective 'prickly rope' I was wondering if you could string on to the rope those cheap 3' sections of 3" or 4" wide plastic mesh that you can get at a big box hardware store that snap over the top of your gutters as a cheap leafguard? If you could zip tie those to the rope and make sure they stay vertical to the water surface the water would flow through those very well and they might gather up the leaves and hold them more strongly than zip tie loose ends would.
Something like this: (about 50 cents a foot, comes with or without the very fine mesh cover)white vinyl mesh
I have never tried this myself but thought it would be worthwhile having some type of labor saving device that would sift off the leaves for me. Maybe a boat mounted tow net?
My leaves float for a few days and then slowly sink. if the wind is right they will all blow to one side and then it is easier for me to rake them out but most of the time I just give up and let them fall and sink. The ones that land in deep water are more of a concern since in the deep water the oak leaves do NOT break apart. Maybe some muck reducer enzymes would help with that. But the hundreds of pounds of dark oak leaves that pile up in the shallows are my chore in the spring to rake out.
At first when I had the pond it was stressful to see them come down and float and know they were going to sink and not be able to do anything about it. But now I've learned to let it be. There is a positive to that bed of leaves in the shallows. The tadpoles and turtles like to burrow in them and they find some very nice insulation that way. In addition, when ice is ready to come off the pond in spring, where the leaves are the sun gets to warm up the bottom faster and the ice comes off a bit faster. This also means that turtles and tadpoles under that bed of leaves are also warming up faster. They seem to like this. I have raked piles of leaves in the late fall out of the shallows and by mistake raked up an embedded hibernating turtle. They do not like this and then they have to get all embedded, slow down their metabolism, and settle in again...
The other plus is that the perch seem to like the bed of oak leaves just fine to lay their eggs on. They do this just as readily or more readily in my pond than on twigs, branches, or obstacles. They seem to prefer either going way up in 6" of water and laying it on the oak leaves, or they will sometimes leave eggs around the base of my stands of reeds or sedges that clump in the shallows. It seems like they like to hook the egg strand on something and that may help pull it out?
So, I can't completely explain the dramatic drop in water level you had with the muck tablets.
My choice has limited info about it but is sold from Wisconsin and was found on Amazon:Great Lakes Bio Systems Muck pellets