Just a quick question if anyone knows whats going on with my tomatoes. I've found nothing definitive with what's going on.

Hydroponics:

Age: seeded 5 weeks ago

Lighting: 400W MH (18 on/6 off)

pH: 6.2

uS: 2000

Tomato plants have been growing great until lately. Just the one plant was affected, but today I noticed it starting on a second plant.

Leaves get little yellow blister-like bumps on the top, greenish/whitish on the bottom. After a while the leaves start drying up and then die and get crispy. I cut off the affected leaves on the first plant thinking the light was too close - I had just switched to MH lighting from fluorescent. Has anybody seen anything like this before?