About 5 months ago, around 2-3k miles I flushed my coolant, but it is already murky and crappy looking. Is this just from po poorly maintaining or do I possibly have bigger issues?

Also, I assume this is part of the problem but I slowly over heat while sitting. Its slower now with the new fan clutch, but should I plan to replace my rad, water pump and thermostat?

 

Very good possibility the PO's maintenance or lack of I should say, can/will cause this. Cheap insurance to replace those last 3 items there, wouldnt hurt to maybe replace the hoses too, that way you are starting fresh with everything. While the thermostat housing and water pump is off this is a perfect time to really flush the engine out.

 

Sometimes if u put in 2 diffrent coolent colors it will cause a muddy foam. If it looks like a milkshake than u have oil and antifreeze mixing.