Most likely you have iron in your fill water, either from your well, or from rusty water pipes carrying water to you from the plant. You can check and see, with the metal bucket test: http://pool9.net/bucket-metal/

Please don't give up too soon. Managing a pool like yours is possible, but there is a learning curve, and thanks to your useless pool store, you haven't been on that curve.

Start by getting a K2006 test kit (http://pool9.net/tk) and by filling our the equipment form (http://pool9/net/pf-equip-form/

. . . membership updated.