It depends how old they are... you said the middle of veg so I'm guessing they are about 4weeks old. At 4weeks some plants are big enough that they can go 3-4 days without any water, so although 6-7 would be a stretch, it shouldn't kill them. Turning the lights from 24/0 to 18/6 will also help considerably. The final decision has to be up to you, it depends on how often you water them now and if they are big enough to sustain themselves for longer than usual (bigger plant means a bigger root system, which can get as much water as possible). So if its a good size and you water at most every other day then i would say that you should be ok.