I Already Have & They Said Since They Don't Carry It Then They Don't Know. If Its Somewhat Similar The Black Gold Then I Think It Should

I'm far FAR from being an expert but I think your tomato plant looks pretty good. My tomatoes always have leaf spots and they tend to grow out of the problems as the weather warms.. Your watering and fertilizing sound fine. You could remove the affected leaves if there aren't too many and then watch and see if it show up on other leaves. Yes, I have heard it is a good idea to remove the bottom leaves if they are touching the ground as that is how a lot of diseases get on the plant. I do it and it seems like a good idea. I see you have some type of watering system, make sure water is not getting on the leaves.

Unfortunately diagnosing plant issues whether they're fungus or virus or deficiency/toxicity is difficult since many symptoms of different issues are identical or very similar. The cucumber looks like a fungus to me but also possibly potassium or manganese deficiency but considering the size of your res and amount of buckets you're running coupled with the fact that your ppm is remaining stable it's doubtful it's a deficiency. The other option to consider is with your ppm level for some younger plants excess potassium can interfere with the uptake of a bunch of other nutrients. So what may look like a deficiency is not really that it's not there for the plant to use but that the plant can't uptake it since, in this case possibly, it's being blocked by an excess amount of potassium. You said you're using MaxiGro which is what I use as well for most plants and is a really good mix for vegetative growth but at 1400 ppm it may have been too much K for the cucumber. Some plants are picky. Most people will do what you did which is just put the plant and the peat cube right in the bucket. And there is nothing wrong with that except for if the cubes get saturated and stay that way they can get mold, fungus, or algae growth which can hurt the plant. Using them is not the issue it's just you need to make sure they aren't getting saturated and control that with water level. I put my plants directly into the hydroton after germination them in a soilless mix. I don't want anything in my buckets that doesn't need to be there. The dampening off that you can get from it usually is just a seedling issue and once plants get bigger it's not a problem. I would just make sure those cubes are staying saturated. What you are doing sounds like a good plan. Flush it out. Start with a weaker mix and go from there. At 1400 ppm, depending on conversion factor, it's either 2 or 2.8 CF. I run my full grown fruiting tomato plant, very nute hungry plants, at 2.6. So that poor brussel spout seedling was getting blasted. Some young plants can handle high levels but other not so much. You're probably going to have to work your way up and find a level that feeds your hungry plants on the lighter side and your not so hungry plant on the heavier side. You're not going to be able to be optimum for all of them. One more thing. If in 2 weeks ppm was staying stable given the same water volume it's too much in my opinion. Everyone has there own way of doing it but I like to see my EC levels dropping on a daily basis. I top up my buckets to a consistent water level and check EC daily. As you noticed when you're water level dropped your PPM went up. Add more water and it goes back down to probably around where it started which means you're plants are using much nutes in relation to the concentration in your res. I like to see a daily drop in EC. Too low a concentration of nutes can cause uptake issues as well as too high a concentration. I like to find that level where I know nutes and water are getting used daily which means I am more in that sweet spot. Hope that makes sense.

KInd of hard to tell from those pics. Looks like potentially fire blight. I assume they are on dwarf root stock since you have them attached to a trellis wire. I see almost zero growth. Looks like you may have had some poor quality trees from the get go. Did you do a soil test prior to planting? Did you water them in when planting and keep them watered? I dont know your location or what your weather has been like since planting.