Pond Boss Forums Thread Like Summary - A few dead critters around the pond

After a conversation with TJ last week we thought maybe I should post this question/observation here and see what shakes loose.
About 2 weeks ago I found a large dead bullfrog floating upright in the pond. Pulled him out, not a mark on it. Thought very little about it, then 2 days later I found 2 dead garter snakes on the bank, also without any obvious marks such as inflicted wounds by a Heron. I also noticed a few (3-4) craws floating in shallow rocks, started wondering what the heck was going on.
I've done several water tests with nothing really standing out. Tests were done last week.
The last 3 days I've noticed more and more dead craws up shallow and today I found 2 leopard frogs just floating dead.
All of the craws I've pulled out have what appears to be an algae-like growth on them. Even though the craw is still solid-fresh dead-it looks seriously like algae.
I have not found any dead fish and this spring has shown a lot of active, aggressive, healthy growing/feeding fish.
One key is craws are all about the same size, I would say "large", so I can't help but wonder if it's an end-of-life thing?
The frogs and snakes baffle me though, both look clean and healthy.
The only water parameter I could say is even slightly out of whack is pH at 8.4. Been there since I riprapped entire banks last spring.
Arrowhead coming good as is pickerel weed, softstem bulrush and seeing a few sprouts of sago.
Any ideas, I've got open ears.

Tonight at feeding time I can assure all there is nothing apparent affecting fish. Tonight the feedbag was on by large numbers of YP from small to Jumbolicious, Monster Male BG, even some SMB were showing up. GSH were literally flying up on the bank, I believe a true feeding frenzy was taking place. Probably the most activity from the biggest fish I've seen since stocking the pond.

My dogs are the biggest source of wildlife mortality around the pond (raccoons, possums, and a big garter snake). I also have one that goes after my BG when I throw food in the pond. Dives off the dock like a rabid wolf, snapping and growling, and then swims around biting the fish food off the waters surface. I really need to take a video of it.