I also have some browning on the lower set they are almost five weeks and dooing great. About a week ago i started seeing the problem somone told me to try epsom salt so i did on three of them and its stiil freekin out i have flushed them already six gal a pot and stayed on water for three days and went back to the nutes. The lower leaves that arent curling or folding are getting brown on the tips n dry . But just tge tips of all the jagged parts and the newest leavs are skinnyier and kind of turning any way temps are good and humidity is at about 52% im ready to feed again what should i do! !!!!!!!!