Brown Leaf Tips - With Photos

I'm using a 42 watt CFL in my grow box.

Until early this afternoon, before her dark cycle, she was in Miracle Grow Moisture Control. I then switched her over to a store brand soil - the only one I could find without slow release ferts.

I've got the bulb on one side of the box about 1' away, and about 6-7" above.

What could be causing this?

dude thats some weird shit i did the same thing I went with Miracle Grow Moisture Control started having those problems and switched over to Black Magic Profesional Potting Soil from Big lots
its most likely from the miracle grow
my plants are still having a little problem with brown spots but I flushed my plants out after i transplanted them and they seem to be doing fine one has a stunted growth and the other is growing fine just like you have brown spots on leaves and now shes starting to get brown spots on the upper fan leaves too
im going to get Fox Farm Nutes in a lil bit and that should prob help them alot

Hmm... I keep seeing things about flushing... no idea what it means. Looks like I have some forum searching to do.

Ugh - not really finding anything about flushing other than people saying they're going to do it... Anybody care to share some thoughts on it?

Does anybody else have any thoughts about this? Was it the soil I was using that caused this?

try looking at the stickeyed topic on plant problems it loks like chemical inbalance

it def is over watering and aeration u need some more perlite