seldomBlue - it is OK to trim the leaves at any point that they need to be trimmed. I trim more near the end when it is more obvious which leaves need trimming. I trim mainly to let sunlight and air get to the lower parts of the plants. Any dead or dying leaves as well.

rcpilot - You have to trim any dead or dying leaves or they will help attract spider mites. The plant should generate plenty of healthy leaves when the nutrients are back in balance.