Should I be concerned?
Yesterday I received my L3+, it seemed to work stable at ~504MH/s. This morning I realized a reduced hashrate, looking at the "Miner Status" reveals, that one blade is not hashing, all ASICs were marked with X.
Luckily a reboot seemed to solve this issue, lets hope it will not happen again...
Are any of the boards showing hardware errors? Keep an eye on the HW errors and watch to see if they are escalating. It is not a good sign when the miner starts to drop boards.

You are right and I whish I could have tested the miner longer. But when my wife went into the Garage today she came back to me and "kindly" asked me to "reduce that noise".
Being afraid that she would take care of it I decided to send it to my hosting center today, so I have to wait a few days before I can continue testing...
Im going to have it in my basement, waiting for May batch.