please help. new flood table set up

OK, I am totaly new to hydroponics. I have a ton of money invested here and need help getting this set up right for he plants i have going now are just bag seed for trial run. I started out from seed, used 2x2 inch rockwool cubes to start. Then put them in a home made DWC set up. Used a 600 watt HPS light at first but have since switched to a 600 watt MH conversion buld. Its a solarmax brand bulb. I have switched from the DWC to a 3x3 foot flood table set up i purchased from the local hydro store. I have been using the "Recipe for Success" kit i also purchased from the local hydro store. It consits of BC grow and BC boost, Thrive in the red bottle, Magical, Root 66, and sugar daddy. I used this at full strength for the flood table. The plants are just over 3 weeks old in the flood table. My grow room is a 10x4x8 area split in half . Use half for veg and half is waiting to be used to flower. I have a 500 cfm exhaust fan pulling air from both sides and vented to the outside. I have a 250 cfm inline duct fan pulling air into the room from a cold air duct from furnace. The room is totaly covered with black 6mil polly, so the room is pretty well sealed up. My 600 watt lamp is about 18 inches from top of plants. I flood the table 3 times a day for 5 mins each time. I put the 2x2 rockwool plants in a 3.75 inch net pot and cover the top of the pot with clay pellet. The flod tray is also filled with clay pellets. I have the cups sitting on the tray and the pellets surrounding the pots. When i checked them yesterday some of the plants look really burnt and shriveled up. A couple of them are still looking good but the root system on all of them is not all that great. I posted pics and tried to be as detailed as possible. I am wondering if this is nute burn or light burn? My temps run high in the room, 85 degrees most of the time wth lights on. The lights run 18 on 6 off, fans run constantly. any input here would definatly be appreciated. Want to get the good seeds going ASAP!

i should also mention my PH has been all over the place. I check it and it sayd 6.8 to 7.8 and then add PH down and get it around 5.3. the next day its up again. The PPM is all over the place as well. One time i check it and it says 600 then again check it it says 1400. I was using well water that i lerned was fulll of nitrates and contaminents. I have switched to RO water and am currently flluching the table with straight RO water only, no nutes.

You know what's wrong, you said it. Stabilize your nutrients. I do not use hydroton so I do not know first hand but I think you need to stabalize it. Did you soak it before your grow? I heard it is a bit hard to keep low. You did not say what you are feeding them exactly. I am assuming you are following the bottle. You might want to mellow it out a bit. You should not even be at 600. I would say 200 or 300 (ecx500) at the stage you are at.
I notice when I feed my plants too little the TDS goes down after a feeding. When I feed them too much the TDS goes up. I like my nutrients to be at a place where there is a very slight drop in TDS. Start small and build your way up till you notice that drop. Check before and after a watering. I would also flush your medium with pH corrected water. Around 5.0 (help stabalize it). Worked for me before. After the flush start small with the nutes and aim for a small drop. Not a big one. No drop is ok too. When it goes up. that sucks.
good luck.
post up how they do. You should notice a change soon.
It is good you at least noticed what was wrong. Your grow looks really nice. Genetics plays a huge roll in the grow, keep that in mind since you put a lot into it. Bag seed might not be the best idea.

Well flushing is the right way to go. At 3 weeks old your plants were not ready for full strength nutes. Go half nutes or a little less than half when you add the nutes.

PH is a daily thing. Keep on it at the same time each day it will level out and not change as much. Good idea to change from tap water to R/O, it may have been what was burning them up.

As far as the PPM's. The only way they will change is if your plants are drinking alot of water and I don't think those little ones are doing that.

If your water was low and you added more tap water then it would go up by how much ppm's the tap water has.

If your plants drink alot in a day then PPM's go way up. You add just PH'ed R/O water and ppm's come bcak down to where you had them. Do not add water with nutes only plain water.

thanks for all the advise. they are lookng a but better today. will give them a couple days and add a low dose of nutes.

Follow what Demo and Loc have told you and you will be golden ..... and since they didnt leave anything for me I'll just say "Hi" :)