I wish I could help but my knowledge of DE filters is limited. But if your filter is rated for 3/4 hp (not a real rating--it's max GPM that matters--how many gallons per minute the filter can take--and what's the max the pump puts out) and you are over-straining it, bad things can happen.

The brown stuff I get is either dead algae or pollen and usually ends in June. But you need a metal test and can either buy one from Leslies on-line or from TaylorTechnologies.com

For metals, again, I'm not the best. Mbar (Marie) is one of our most knowledgable members, and she usually can help diagnose metal problems and recommend a solution.

Meantime you need to post your standard test numbers:
FC, CC, pH, T/A, Calcium and CYA. If you have them, copper and iron and magnesium numbers as well. You should vacuum to waste as well.

Poconos or one of the pool dealers here can advise you on the pump and DE filter situation.

Don't give up! It's definitely solvable, and without a pool service to muck things up.