I don't compost any of my tomato plants, healthy or diseased, I pull them all after first frost and dump them in the pasture for the horses to eat. And I rotate the tomatoes from one end of the garden to the other every year- and since I added a new corn patch this year it will be a three year rotation. Between that and pruning the lower foliage to prevent soil contact and using drip irrigation (and living in an area with almost no rain in the summer) I haven't lost a plant yet this year and all 40 tomato plants look very healthy.

Septoria leaf spots are taking over my tomatoes this year too probably facilitated by the nonstop raining. The variety I observed so far (in my garden) that resists the virus are Cherokee Purple, Aunt Ruby German's Green, Cowlick's Brandywine and Kellog's Breakfast. They grow right next to the ones that suffered from it.

Re: the nutrient issue-- there are folks who post here who grow hydro who may see your post, but I would also ask the hydroponics forum in the meantime. The pale leaves with still-green veins looks like an early nitrogen and/or mag deficiency, but hydroponics is a whole different deal than growing in soil, As for the lesions... It doesn't look like spray damage to me, and it doesn't look much like Septoria. It might be the start of the concentric/target pattern in other diseases like EB or target spot, and botrytis is also a possibility, especially considering the paleness of the lesions. I did spray with a fungacide to kill aphids. Is it possible the fungacide spray caused this? Aphids are not fungus. I guess some fungicides may be somewhat toxic to aphids, and the simple physical action of liquid being sprayed and running off is good at knocking back aphids because it washes them off. A lot of people use just plain water and squirt off the aphids with a vigorous spray. That approach tends to work best outdoors, though, where there are beneficial predators to clean up many of the straggler aphids. If you continue to have aphid problems, you'll need to get something like insecticidal soap to more directly and efficiently address the aphids. Fungicide is an inefficient way to kill insects if it is effective at all. EDIT: if you're using neem, it can work on aphids AND fungus. That said, you apparently needed a fungicide anyway, so it worked out for the best. Are the spots limited to just the leaves in the photo or has it spread to other places on the plant? If only on the leaves in the photo or just a few leaves here and there, I would document well with photos in case you need to refer to them later, prune off the affected foliage, and repeat fungicide application in a week or so. What fungicide are you using?

In your zone (which is also my zone), Mother's Day should normally be more than fine for planting out. But both last year and this year, we had a very wet, cool May. Last year some of my plants also got speck very early, during May. Replacement plants, however, that were very small and young when they went into the ground, caught up to the older plants easily after a few weeks and went on to produce just as much. Those didn't go in until after the first week of June. Of course, we also had warm weather until late into fall, with a killing frost not hitting until November. This year, I'm deliberately planting late. I have some tomatoes planted out, but not all yet. The Drowns who run Sandhill Preservation in zone 5 IA say they now start their tomatoes in mid-May and put them out in mid-June (!!!) because they see less disease, and they still get plenty of tomatoes. I'm a little too impatient to get tomatoes to wait quite that long, and we're a bit warmer here, but around the Philadelphia area, older gardeners still say Memorial Day is when you plant out tomatoes. The race to boast the earliest tomatoes may not be worth it here (well, not yet), since we're still not racing extreme heat and pests the way more southern gardeners are, and we do have a rather long growing season, unlike more northern gardeners. Anyway, the short version is: I don't think you need to wait longer, but if you do, you'll have to spray your plants frequently during May if we get a lot of rain again. Or you can wait and set them out later. But if you go that route, prepared to be constantly tortured as others post beautiful photos of lush tomato plants they put in the ground early, LOL.