sorry about the link, i just realized I'm not supposed to do that.

You're not? I don't know about the actual rules, but it seems to me that if you have a website that has content as well as a store, there should be no problem. Who knows more about a subject than those whose livelihoods depend on it? Now, if you were obviously attempting to use subterfuge to drive traffic, you came off as a used car salesman, or your main intent was obviously only to use the forum as an advertising tool, I'd understand people getting irate. If someone wants an infrared thermometer to measure nute and medium temperatures, I'm sure as heck not going to send them to my competition when I know that I will give them better service and free advice on applying IR practically. I'll also direct them to my website to see what I carry. Of course, I've never had reason to do so on here.

On my first try with hydroponics I used a DWC/NFT hydrid with similar results; some early good looking growth, then suddenly the plants went ka-pooey.
Here is what I think happened. my water intlet (from the rez to the trough) came in at the top. Since the system always maintains a certain liquid level, that meant it drained from the top also. When this happens the aerated solution(assuming it is aerated)floats across the top of the trough without actually mingling much with the lower nutrient levels. This is called laminar flow because the fluid has a layer (or lam) that floats above a lower layer.
The problem that develops is the lower level of nutrient solution eventually loses its oxygen and goes anaerobic causing massive root decay. Since the plants don't know better, the bulk of their root system is in the dead zone and so the plants eventually don't have a large enough root system to support the full grown plant.
Now I can't speak to your system as I don't know what it looks like, (or rather I can't tell that well from what you posted on the other thread) but that was my first and last attempt at a DWC/NFT hydrid.

here another pic of my little system, that is teh same tomato plant in the middle on top..two weeks prior, the growth was amazing.

i made the mistake of buying clear tubing, i was at lowes and thats all they had in the size I needed. lesson learned, it's an algae breeding ground.

my tomato plant seems to be coming back from the brink, the leaves have perked up and it's looking much better.Hopefully it comes back and at least produces some fruit

You have a black reservoir and you're in Florida. It seems to me that you might want to consider at least insulating and shading it or even burying it in the ground and shading the lid.

Brown roots don't always mean root rot. You can usually smell a bad smell if you have rot. Sometimes brown roots mean they are covered in salts. That will dehydrate the plant in the way you described.