water with epsom salt(1tbs disolved in 1 gal water),i dont think you have to flush since you were giving it a modest amount of fertilizer,the ph is ok at 6-6.5,the mg will bring it up slightly,add a little more phosphorous on the next feeding,the humidity is low because of the hot air,i would just use an outake fan for now and one on the plant,the outake should be able to draw in enough cooler fresh air air,Im sure you're diagnosis is correct also,it will take several days to see an improvement,if the low humidity is still a problem,a shallow container with water in the area should help,good luck to you an post the results....bonbon