it can be anything my friend, without additional informational my guesses are: mites; nute burn; incorrect ph; overwatering; fan burn. did u leave drops of water on ur leaves when u watered? did u use excess amounts of nutes? good luck.
Nutes half of suggested....no fan. Kitchen window until outside ( outside only on sunny days as if now...water twice a week. In solo cups so. Just a little...no ph. Tester available as of today..
