I am sprouting my vegetable seeds indoors for the first time and so far, it is very successful. I have lettuce, carrots, cucumbers, basil, oregano, and thyme. I am using grow light bulbs plugged into a cheap light fixture for light. Most all of the seeds have sprouted and range in size from about 2 inches to 4 inches. The cucumbers are the ones that are 4 inches and everything else is around 2 inches. How do I know when to transfer the seedlings from the jiffy pots to slightly larger size pots? I know they need to be hardened off before putting outdoors. The last frost date predicted for my area is April 10, but I usually wait for several days after the last frost date because of surprise frosts.