Soap is the issue as well.
Front loaders do need front loading *less sudsing* detergent. I even cut my down by 1/3 even when using HE.
It's also good practice to run more frequent HOT washers with bleach and a heavy load with front loaders. This helps to get maximum water fill to clean as much as the *tub* as possible.
A forethought, as some machines are semi-tweakable, like my Miele, but if you can get in the service menu, increase as much water usage as you can IMO