Im not expert but isnt a 3/4 hp motor a little small for a sand filter on a 24k gallon pool? If it worked in the past i doubt that its your problem but it does seem a little small. I recently had the same issues and figured the sand was just old. I ended up just replacing the filter and putting in a new pump. I increased the pump from 3/4 to 1hp and it looks great now (i used just shock, yellow out and chlorine tablets)