"Indoor under humidity tents" can mean lots of things so more info is needed.

Normally transplants are only contained in a humidified environment just until the seeds germinate/sprout. They are then removed to a normal environment with adequate air circulation. Growing transplants in a humidified environment only leads to the development of damp-off, a fungus infection that can quickly infect and kill the plants.

That may be the issue you are dealing with.

Dave

Here is a link that might be useful: Damp-off FAQ

It miight be too cold yet in zone 6 for those 2 plants to be outdoors.

Hi,
I've been using a homemade orchid mix which drains and dries out incredibly fast. I do this to avoid the dampening off disease.
The leaf tips are turning white before the leaves finally dry up and die. Does anybody know why the leaf tips are going white and how to keep the plants from dying?

thanks

I think It just might be to early for pumpkin I useally plant mine in mid June. But I'm in California. They might be stressed from the transplant. I would try putting them in a dark area for a couple of days. might promote the plant to search for light and increase growth a bit.

If you are using an orchid mix that dries out incredibly fast that is most likely your problem. It dries out before your plants have a chance to take up the moisture. Under the humidity lids the moisture hangs around until the plants take up the moisture it needs but once out of the lids it can't get enough When you transplant put them in a good soilless mix that has good drainage like pro mix. Damp off doesn't come if you water properly. It comes if you overwater.

Cucumbers do not have to be started ahead. In my zone 3 they are fine growing from seed. One year I planted my greenhouse grown Cukes and next to them I planted seed. 3 weeks after the sprouts from the seed were up both were the same size and produced at the same time. Now I never prestart Cukes