Track the gross profit margins for each of your customers. Line those percentages up from high to low and then make decisions to correct the worst (i.e. bottom 5%, bottom 10%, all margins below 5%, etc.). See where you can cut costs or if pricing is the problem. If necessary, raise prices ASAP unless there is a contract in place. Raise prices on contracts where you can and whether they accept the new higher price or not, you will make money. Because of your actions addressing the bottom gross profit margin customers, your overall gross profit margin % will rise and you will have more time to work on profitable customers.