unless you've got bad 10m90's (I've never come across any) I find it peculiar that both seems to be acting up
pull out one 10m90 and test it with a DMM at ohms, test drain-source:
short all legs, before measure drain-source => very low ohms
if you don't get that the 10m90's are probably bad
if you have a breadboard you might find it useful to build a cascoded css including the trimmer, and test as previously described.
If you can't adjust the current using the trimmer, the DN2540 is probably bad (I've seen that a few times)
Or you can use an 8pin IC-socket with resistors+trimmer soldered to build a bug-style test CCS-fixture.