I think you'll find that once everything is dialed in, hydro is easy and fun. You're just in the learning curve at the moment with a couple set backs, no biggie, happens to everyone eventually.

Lets go right down the list. I'm sure you can get this corrected before you lose your crop.

Fix that temp! Don't let the reservoir get above 70F if possible. If you have no way of cooling down the res, try filling a couple gallon milk jugs with RO water spiked with 1ml of PH down in each jug then freeze them. Put those frozen jugs (with the lid off) inside the reservoir. This won't cure the res/temp issue, but it will help stabilize it during long hot periods and as the water in the jugs melt, it will help dilute your brew and it will help adjust your ph slightly.

Keep that PH stable too. I would make damn sure that your ph tester is accurate and keep it as close to 5.8 as possible. DO NOT let it hit 7 or above. Don't push it too far down allowing it to climb again either, that becomes too unstable. Keep it at 5.8 even if you have to wake up in the middle of the night to adjust it. Use only a pro PH down (like GH PH down). They're more capable of stabilizing PH than vinegar.

Make sure you have a good exhaust fan pulling air out from the top of the room. Keep your room at 80F or below if possible. Plants can tolerate temps up to 90F but prefer around 80. Add a circulating fan as well so you don't get hot spots in the room. Have the circulating fan blowing between the plants and the lights (don't put the fan right on the plants).

In my opinion, your ppm is too high. A sick and suffering plant only 10" high probably can't take advantage of that much nutrients. When my plants were exhibiting those characteristics, I put only PH adjusted water in the res and flushed the plants (3 water cycles on a flood and drain) then made a new brew. DO NOT put the full strength of nutes in the reservoir when you make a new brew. Instead, add 1/3 of your brew to the res water, next day....add 1/3 more with water...next day....add final 1/3 with water to top off. This way you introduce the nutes more gradually to the roots/plants avoiding burn and shock.

If the light is too close to the plant, back it off. The heat and light might also be more than the plant can tolerate in its current condition.

Finally, as far as the nutes go, I would abandon your current batch and start over....a quick flush with PH adjusted RO water only for about a day. Then after flush, use fresh RO water having zero ppm, add your calmag+ first and bring your ppm up to 50 taking notice of how much calmag+ it took to reach 50ppm. (Tap water is usually around 140, which will be the 3rd day target for the calmag). Then add your nutes bringing the ppm up to a total of 300 the first day. Day 2.... add as much calmag+ as you did the prior day then add more nutes on day 2 bringing it up to a total of 450ppm and on day 3 add as much calmag + as on first day and top with nutes bringing it up to 650ppm. Run that for a week and when you notice a brighter green in the new growth (not yellowing), then you know you're on your way to recovery. Next water change, use the same technique with higher values.

When you said you had shiny spots on the leaves, I assumed that these shiny spots are heavy dark, or heavy bright green in color. This is what I've witnessed in cases of over fertilizing. The shiny spots soon turn patchy and eventually turn to rust. I also found that a pale light green color usually indicates it's time to up the nitrogen.

I will finish by saying I am NOT a hydro expert by any means. I am on my first hydro grow, however, my experience in simple plant health and your description of your situation suggests that you are working your plants too hard.

In my opinion, it's better to back off and not push a sick plant. It will recover if you nurse it, then you can push it after recovery.

GM