hmm, i can't really tell what's the problem from your description. you can try adjusting the pickup heights first. there is a guide on dimarzio's webby,
http://www.dimarzio.com/site/#/faq/ under orientation and height adjustment. if the problem still persist, it may be wise to spend a little cash on a good setup by a qualified guitar tech.
Quote:
How high should I adjust my pickups for the best sound?
There is no specific distance that works best for everyone. We measure string height from the top of the polepiece to the bottom of the string when the string (usually the high or low E) is held down at the highest fret. For standard, full-size humbuckers, a reasonable starting point for the bridge pickup is at least 1/16" (1.5mm) from the high E and 5/64" (2 mm) from the low E. There are no recommended distances for the other 4 strings. Their polepieces should be adjusted (if necessary) by ear in relation to the volume established for the first and sixth strings. Once the bridge pickup is adjusted to a useful distance, the neck pickup can be adjusted by ear for a good balance.
For single-coil pickups and all hum canceling single-coil replacements with Alnico 5 rod magnets, we’ve found the following formula works very well: at the highest fret (usually the 21st or 22nd), the closest recommended distances from the top of the magnet to the bottom of the string are:
Neck and middle pickups
low E 1/8” (3.2mm)
high E 3/32” (2.4mm)
Bridge pickup
low E 3/32” (2.4mm)
high E 1/16” (1.6mm)
What happens if I adjust my pickup too close to the strings?
The closer the pickup gets to the strings, the stronger the signal that's sent to the amp. However, getting a pickup close to the strings brings the magnetic field closer, too. If the magnetic field is strong enough, it alters string vibration enough to make the guitar sound out of tune, and it can also cause string buzz and reduce sustain.