Hello ROOD...

Sounds even MORE normal..

It is very very difficult for a 600 watt bulb to provide enough LIGHT (lumens) to the lower foliage of a 3.5 foot plant... especially if you have more than 1-4 plants. This is why your lower leaves are prematurely turning yellow... Although, I am very suprised you made it to week 4 without yellowing.. I think you have done very well!!

It may not even be premature.. : )

iloveyou

How far is your light from your canopy (foliage) ?

iloveyou