novice gardner with tomato issues

[pyxiestix]

hi new here & i'm hoping you all can help me.

i've just planted my tomatoes about a week & a half ago (greenhouse started - we bought them @ about 4-5 inches tall) i have roma, hillbilly, celebrity & sweet millions. i noticed a couple days after planting that they looked odd...the edges are turning white & drying out & eventually killing the whole leaf. some have suggested sunburn but new growth is doing the same thing. others have suggested powdery mildew - but there's nothing powdery about this & it looks nothing like the pics i've seen of it. i'd love to find out what's going on soon - it seems to be spreading...i've noticed a few white spots on my watermelons planted near by. we live in central ohio (zone 5 i think).

it's getting worse & it's much more widespread than it was when i took the pics a couple days ago.

HELP!!!