Sounds a bit fishy to me. what is the kelp accomplishing? what did your soil test show I guess?

Any black streaks in the wood of the broken branches?

I've been noticing with most of our trees (we have a lot of ash, well we DID until the emerald ash borer that is) that we have been getting a lot of lichens that are growing not just on trees but on our roof and siding too now, indicative of more acidic conditions, possibly. I blame the aluminum oxide being sprayed by chemtrails. Anyway, I would check the Ph and see if it is too low, that may be the problem. Our one ash tree that is doing well (even though others are dying as well as many other trees- cherry, box elder, etc) is not shaded by other trees and I have been getting rid of the lichens by throwing wood ashes on the trunk as far up as I can. The tree seems to be doing well so far. Is your sugar maple being too shaded or does it need more nitrogen? I would do a soil test at least. Or check out bach flower remedys if you are more of a back to nature type. Hope this helps!