Brown Sludge on Coolant Dipstick?

[Mikaelisu69]

Pulled my coolant dipstick out yesterday and noticed a brown sludge on the lower part of the stick. (5.7 hemi) Almost like a dark applesauce consistency.
Engine has only 16k miles.
I may have topped off the tank last year, honestly can't remember, with a standard Prestone coolant. Thinking this could be the cause?
Coolant temp runs normal at about 201 degrees.
Does anyone else have this brown sludge on their coolant dipstick, or did I cause this by topping off with a non-OEM coolant?

Just checked mine and it was completely empty with brown sludge on the dipstick. Only have 31,000 miles and had the engine replaced at 11,000 miles because it was using 1 at of oil every 1000 miles. Been to the dealer multiple times and assumed they were checking fluids but I guess not.

 

[HSKR R/T]

Fwiw my truck, with 75k miles has a completely clean coolant dipstick. I have had to top off my reservoir once because it was low enough dipstick was dry.

I also still get the coolant smell on hot shut down from time to time.