Never wash them on HOT. It potentially damages the fibers and so does drying them in the dryer for prolonged periods of time. You most likely toasted the fibers.
Always wash on short cycle and cold water.
i disagree with the hot water part. boiling microfibers has long been a treatment for towels with certain conditions, and that water is a lot hotter than the hot feed in your house for your washer. i wash all my towels in hot and never have any problems...and they are very high quality towels, almost all microfiber madness at this point.
the recommendation for soaking in Power Clean and hot water is a good one. my first remedy recommendation would be a machine agitation and then soak session in oxi clean (powder
well dissolved prior to adding towels) and hot water, mainly because it's so cheap and effective, but that isn't for everyone and we know APC will work. i have an older 80 series washer that allows me to soak things, add stuff whenever i want, etc. i know some machines are not friendly with that process, but there are ways to do whatever you need such as the bucket soak mentioned above, etc.
also, i used to hang dry and have found machine drying (i use automatic and i believe it doesn't say high or low heat, just more dry or less dry - everyone's machines are different) is vastly superior. i've had WAY less linting and just overall better experiences with my towels now that i machine dry.
it makes sense because i think hang drying leaves more opportunity for anything in your household water to stay bound to the fibers. i do have a very comprehensive softening system for my household well water but the fact remains that it goes through pipes, sits in the water heater with a sacrificial anode, etc., so the water is always going to have solids in some capacity.
