I am having trouble with my pour. I fluxed the lead and removed the impurities but after pouring several jigs the top of the lead become a red color and my pour is not consistent anymore. Could it be the lead that I am using is really dirty? Any tips or advice for getting a good pour or dealing with dirty lead?

There are a million possibilities.

Is the lead hard or soft?

Are you doing cold pours first?

Is the mold hot?

Use mold release.

Are you pouring with a pot , hot pot or a ladle?

Is the air trapping the lead from flowing? Add vent Lines

Crack the mold to see if that helps.

Tilt the mold left to right, top to bottom to see if that helps.

This is just a start, if you would like more help PM me and we can discuss further.