hard to say, but if this is an issue with EVERY mix you do, than you should check your room acoustics, or soundcard, mixer, or any module your signall path involves,maybee some odd default settings which affecting the sound, etc, etc, i know the 1031's very well and there are absolut awsome monitors in that range... and should
"tell how it is"
also a good solution is to listen in the morning to your mixes, specially for finalising, as your hearing , specially the high frequency spectrum goes down over the day, even more after long hearing sessions.
hope it helps.
a.

I got exactly the same problem.
i must record with too much lows or i don't know because most of the time I don't cut highs off unless it's disturbing but more on bass-mids and when the mix is at the "end" it lacks highs above 4-6kHz even though the rest of the spectrum is well balanced. I don't know how to improve on that because even when i record only direct (through my fw1884 di) it comes to the same.
but then when i add the highs afterwards it sounds good...

actually this post made me think a bit...(happens sometimes)
i wanted to see how it is in reality (is that so) so I took a spectrum analyser (cubase native one) from the dust and compared before and after and also compared with other mastered work of good facture .... i compared with analog style music i'm doing, that is mostly rock-punk-hardcore-metal
a few points came out:

1- even if I add the highs afterwards in the spectrum analyser it doesn't change that much in the spectrum (even if when listening the change is dramatic...)

2- compared to the other mastered work, my levels (when adjusted) from 4kHz and up are far lower than those even if the rest (0-4kHz) is almost equal and if I raise more highs it becomes harsh and horrible

3-another thing i saw was that on the frequencies between 1kHz-4kHz I have a lot more peaks than the others like it's going up and down like 50 times but on the other it's like just a few big fat peak or almost no peaks depending

so now comes the questions what is going on?
I know that from the start of the recording process it should be well balanced and I'm going to try to make it better next time but i'm not really sure how to achieve it
for point 2 is that the cause of bad equalizer? or maybe not enough compression?
for point 3 do they compress so much that there is no difference between frequencies?

I hope some knowledgable person will help us out and i'm grateful in advance (even if i'm already 'cause of all the good things i learned on this forum.. :)

Don't forget about the arrangement. If the project is comprised of instruments sitting in the lower octaves without too many upper overtones, it will sound unnatural to hype up the high end. However, if it is a busy arrangement, consider pulling down some of the lower end of some of the instruments (maybe the cymbals). Then you could bring those instruments a bit further up in the mix without burying or muddying up the other needed tracks.

-Erik

I-Quality wrote: 2- compared to the other mastered work, my levels (when adjusted) from 4kHz and up are far lower than those even if the rest (0-4kHz) is almost equal and if I raise more highs it becomes harsh and horrible

Maybe we have just "bad highs" and your ref. material has "good highs"... Hmm... So the gain of our highs makes the song sound harsh, and their highs makes the song sound bright...

I'm going insane...