What the heck is that soil? Do I see WOOD CHIPS in there? Yikes.
Yes, when you are flushing plants indoors, you need to be certain that the soil is light and loose and there is no chance of standing water.
Leaving water in the drip tray was a mistake.
In the future, it is good practice to drill extra holes in the sides of the pot using a 1/2" paddle bit.
What I am seeing there, and since I don't know your soil pH I could be wrong, but the combination of excess moisture and acid soil is DEADLY to plants. That barky looking dirt needs to be checked.
Also, even in optimal pH conditions, saturated soil pretty much disables the roots from uptaking nutrients. There is too little oxygen, and the root zone goes from healthy oxidizing conditions to unhealthy reducing conditions.
Go find a paddle bit, drill holes in the pot, RAISE THE LIGHT, and run some water through that soil to check the runoff pH. Adjust if necessary.

Edit: Cyberlink and Techieboy, are you the same poster with two identities?