you are more than likely facing one of three problems 1.) you may have to back off on the feed the plant is recieving sounds a possible overfeeding problem to me. 2.) your humidity is too high can you possibly get use of a dehumidifier. 3.) if found out its not an overfeed problem your root system uptake may be locked up try a direct foliar feed with a dilute solution. and one more thing that springs to my mind is bugs, closely inspect all leaves and undersides to clear possibility of bugs sucking juices from your leaves. hope ive found your problem !