Depth is the problem. You need to use the foam tips and insert them deeply. Just like the ety they can be easily inserted much deeper than you would think. This cuts the treble peak down more than half and I don't hear any subdued treble at all nor peakiness. I find the treble boost they have to be slight. With the silicon they are too peaky, but I don't use those. I'd say silicon = peaky, foam = less peaky, foam inserted deeply = no peakiness, but just a slightly more forward treble.
This is somewhat correct, as seen on the measurements done by GoldenEars, but I'm not too sure about treble being more forward. Maybe it's because of them being closer to the eardrum, raising the sound pressure level.
However I'm not too sure if one can insert them deeper at their reference plane, as it's form factor is made that way. I wonder if changing tips into longer-stemed ones, such as Westone Star Tips, would help.