I see a couple possibilities.
One, toxic salt buildup/low pH/cold wet soil combination. I don't know where you are, but in the northeast US we are finally getting low temps and if you want to see a plant act sad, put it on a cold floor in a cold room and overwater it. The flushing way have contributed if your soil was not free-draining enough. Cold, wet, soils make ANY problems look much worse, and pH problems are the WORST combined with low temps and excess moisture.
The other one is overdoing the bug spray. I'm not sure what you are using but you should as general practice make a light initial application and raise the lights, then watch to see if your plants are okay after a day, and THEN bring light back to full intensity.