Yes, Coon wrote episodes under the name "Lee Cronin" during the third season (for contractual reasons). He wasn't on staff, however, which meant he wasn't around to do re-writes.
(He actually left during the second season; John Meredyth Lucas assumed his role for the remainder of that year.)
Yes Bill J, that's an extremely good point. But each script did not get "polished" as before. There are a lot more rough edges. The scripts seem to have less depth, only surface action, not the multi-layered character interaction we had seen before, IMHO.