My tomato leaves are drying up. They have plenty of water and it's affecting only one variety. I've been hardening them off, could it be from the light? Heat isn't an issue yet. Could it be from my artificial lights? Or could it be because they are getting root bound? I know they are but they have to wait until tomorrow to be transplanted, we have a frost warning tonight. They have been fertilized with diluted fish emulsion and seaweed extact weekly, should I cut back or dilute more?

Or is this a disease? What can I do about it?

Thanks a bunch.