Mine are being very picky, too. They have snubbed any colour of pepper for about 3 weeks now-just my luck it is cheap at this time in UK! They are reluctant with red AND green oak leaf lettuce, round lettuce and romaine. Sigh.
Mine have never been that keen on carrots, full stop. They eat them sometimes, but mainly they are left until the last in the bowl, and the alternating dirty/begging looks begin.