You have had nitrite reading of 0.25 for some time now. I would suspect this reading. Maybe you have a bad tester, maybe it is hard to compare colors on the chart or whatever. I would have it double checked by another tester, LFS will do this for free usually. If this reading is verified as correct then you need to wait a while longer for it to go to zero before adding anything. If it is proven to be wrong, ie. the reading is actually zero, then do a 20% water change to bring nitrates down and go ahead with some CUC buys.
JMO FWIW