Hello and

The Florida quarter looks like something acidic may have splashed on it.
The second quarter -- can't quite read the year -- looks like it spent quite a bit of time in the dirt.
The Conneticut quarter looks like it spent lees time in the dirt. A sintered planchet would not have the lighter/brigher areas. It would all be the same color.
The nickel looks normal to me. What are you seeing? Did you mean '
Grease Filled Die'?