sick cilantro, bolt, measuring second shelf temperature

I think I've been overwatering the cilantro.  The problem with an overwatered plant, is that except for the soil, it can look a lot like an underwatered plant, or an overheated plant.  Here's my wilty cilantro as of yesterday morning:

There are a lot of yellow leaves, some with brown edges, others with brown stems.  I had been erring on the side of overwatering the seedlings since I'd found some of the tomatoes looking particularly wilted after going more than 12 hours without water.  But I guess that was a few weeks ago, and it's probably time to start spacing out the waterings a little more.  I haven't watered the cilantro since yesterday morning, and am going to wait until at least tomorrow morning, even though the soil now looks quite dry.  Hopefully they'll be able to recover.

During my research into causes for droopy cilantro, I found out some interesting information about the plant.  I'd like to amend a previous post where I jokingly attributed the "Slow Bolt" name for the cilantro seeds I planted to a comparison between how long they germinated and how quickly they grew.  I now know that "bolt" actually refers to an herb sending up a flower stalk.  The flavor of the leaves often changes after it has flowered so bolting is undesirable, and the slower it happens, the better.  Cilantro in particular bolts due to temperature increase, typically when the soil temperature rises above 75F.  I didn't take that into consideration when I chose to plant it on the cooler top shelf and in a tray without a seedling mat, but it's good information regardless.  It also helps me rule out underheating as a cause for the wilting plants.

In other temperature related news, I'm starting to worry that the plants in the second shelf might be getting too warm.  They are closer to the electric heater meaning increased air temperature and are also on top of a seedling mat meaning further increased soil temperature.  I put the USB thermocouple on the second shelf yesterday evening, and am planning on letting it collect data until tomorrow night.  It will be interesting to compare these new data to those I collected previously from the top shelf.