[Alan Wheeler]

Diesel "bug" can often look like a rusty brown sludgy slimey gunk. It can be very common for it to grow in only a few places. Like the filters only. The tank maybe fine. Of course, it may have come from the drum or source further upstream and the filters have trapped it. If the engine is running OK, I doubt you have an injector issue. Just ensure the filters get renewed and the housings are well cleaned. Check the lift pup. Inside there is often a fine screen. This will clog up. Remove and clean if there is one. Dose the fuel tank with a Biocide to kill any growth inside. If the tank is easy to remove, then a simple clean would do just as effectively. I would still consider doseing both your tank and your storage drum to ensure both are free from future growth and the big trick is to keep water out of both tanks. No water! no growth!