Last year, I had bottom watered all the time. Since I had a bunch of trays seeded, not germinated yet, and a bunch with good sized seedlings, I got lazy & was misting or top watering everything....ooops. Went to transplant some bacopa & diascia and they were bone dry the bottom 3/4. Check the tomatoes & petunias still in the seed trays and the same. I didn't realize how important it is to bottom water when they are still in the seedling trays and are starting to become a bit bigger. In the small cells, they seem to dry out instantly when to plant roots reach the bottom. Once I get them into a 3" pot, the moisture level should be easier to control.
Bottom Watering for seed trays
Good thing you caught it before it was too late. Eeeks!