italianx, if you're bottom leaves are turning yellow you probably need to give a little fertilizer. This is different from leaf tips turning brown after fertilizing, which probably means the grower has given too much fert. On your fan, you put a fan in there to exchange air, bring in CO2, control temps, and to knock plants around a little, make them wiggle. The wiggling will cause the stems to strengthen so they will stand up straight as they grow. Otherwise, they will fall over.