1) No experience with hydro ferts. However, Phosphorus is the P in NPK. The old teaching rhyme goes 'Up, Down and All Around'. Nitrogen stimulates top growth, phosphorus is for roots and flowers, and potassium is for all over vigor. So, with seedlings, it makes sense to give them a good root system--that's how they'll take in water and with it vital nutrients, and flowers are where tomatoes come from.

2) Grass clippings. I used to have drip hoses in the beds but the new dog chewed them to shreds when she was a puppy. I don't know if I'll be replacing them. I'm not really heartbroken over the loss of the hoses.

3) I planted seedlings last week, they barely had their true leaves. I do it each year--get them in young and they start getting their roots into the ground immediately. They were germinated outside. I do provide minimal protection from critters, bugs and birds. I cut the bottom off a water bottle, toss away the cap and push it into the soil around the seedling. When the seedling has leaves large enough to touch the bottle walls then it gets tossed in the green bin.

4)Not knowing the variety I'd have to say its their plant food.

1.) I use no hydroponic fertilizer at planting, I do sometimes throw in a little granular organic fertilizer in the hole at planting time - mostly for the beneficial microbes that are in it (tomato-tone). As far as organic fertilizers not having enough (plant available) phosphorous, that may be true, but, according to my soil tests, my soil has an excess of phosphorous so I am not really concerned about that; As an aside, I seem to remember reading that phosphorous-deficient soils are fairly rare.

2.) I layer mulch throughout the year, I use bales of hay in the early spring - generally March. I layer it deep (about 3 bales for 200 sq. ft.) and let it compact a little, then I plant through it some time in April / May. As the mulch breaks down I add some more hay some time in mid summer, generally around July. At the end of the season (November-ish), I clean up the dead / dying plants, pull the cages up and mulch heavy with stockpiles of homemade compost, and grass clippings mixed with leaves. I basically use whatever yard waste I have; I even steal some leaves from my fathers oak trees - he doesn't mind :) I use drip tape for any supplemental watering - I put it on top of the soil two years ago, and now it's been covered by a few successive mulch layers - has been working great so far. I recommend that you use mulch of some kind, but if you get lots of sun / really hot summers, and you want to use plastic mulch, I'd put some straw or hay on top of it to keep it from cooking your plant roots.

3.) I'm still conflicted about planting out tomatoes early. I'm very skeptical of weather reports, but I use them, plus a little bit of experience to judge when to put out my plants. With putting them out early you do risk losing your plants, but with my growing season, I just keep back-ups because it's worth the risk (in some cases) of losing a plant for the gamble of getting good warm weather early and getting tomatoes some time around July instead of August. I put my plants out on May 1st; So far the gamble is paying off since the weather has been great since then. All that said, if you're not sure about the weather, won't be around, and don't have back-up plants - I wouldn't chance it, though.

4.) The blue green leaves are more than likely indicative of the fertilizers they've gotten. High nitrogen will give that deep green, sometimes blue green, coloration.