leaking plenum

I have a relatively new AC installation in our Houston, Tx home. Its a 3 ton 13 SEER 410A system installed by a licensed AC company meeting all pertinent city codes. When our weather began to stay in the 80's day and night (common for these parts), the AC began to cycle on a daily basis. A week ago, I noticed water dripping from the ceiling underneath the AC unit. I went into the attic to see what the trouble was. The condensate lines are clear and draining properly and there was no moisture in the overflow pan under the evap case. But under the plenum was another story. I cleaned everything up, put towels under the plenum, then pulled the side cover off the case coil. the moisture is draining well and flowing down the edge of the pan to the case drain and down into the ptrap. Even though the case coil is level in both planes, I decided to tip up the farthest corner from the drain just to see if it made any difference. No change. Thinking that maybe the plastic catch pan under the A coil itself might be cracked, I took the bottom edge screws loose from the coil case to see if any water went into the overflow pan. And again, no change. So....??? Any other ideas before I call service ??

leaking plenum