After reading up on what causes the leaves of tomato seedlings to turn
purple, I learned it was a phosphorous deficiency caused by (among other
things) cool temperatures. I have heard it will go away on its own when the
temps warm up.

HOWEVER, my purple leaves are starting to turn a bit crispy. When I touch
them, they are very dry and want to flake away.

Does anyone know if this is also phosphorous deficiency, or if it is
something else? Will the leaves turn purple and crispy if I water too much
(which I suspect I may be doing)? The seeds were started in Jiffy peat
pellets, and moved to Jiffy 2" peat pots with Miracle Grow organic potting
mix, which I set in trays and water from the bottom. I have noticed that
when the pots are very dry, the plants wilt, and when I water them, they
usually perk up (unless they were too far gone). So I try to keep them
constantly damp, but might this be TOO much water?
--S.