Whats wrong with my seedlings?

Hello all, this is my first grow, and am having some seedling issues. These little guys were planted into the rockwool on December 17th, which puts them at about 18 days.




This is an indoor grow with temps in the range of 72F-79F. They have a heat pad under the tray as they get pretty chilly down there. There is one circulating fan blowing over the tops of the seedlings. Light is a 600w hps with the dial turned down to 360w (dimmable ballast), and it is very high above the plants. Probably 5'. This is the only light I have at the moment.

I am watering when the cubes feel light to the touch. Almost every day, sometimes every other. I watered with straight PH adjusted water for the first 2 weeks, then switched to the Technaflora kit. 1 gal of water and 2 tsp of Root 66, and 2 tsp of Sugar daddy. The main issues are the leaves are browning/yellowing at the tips, bending severely, and seem to have very weak stems. Once they are showing roots through the bottom, the idea is to put each of these in their own DWC 5 gal bucket.

I read parts of the stickied threads on plant health, and it sounds like over/under watering, and maybe too much nutes. Although, the plants did look like this before the nutrient solution was introduced.

Any help would be much appreciated. Thanks!

take heat pad off they look heat burned or nute burned dont give nutes yet

i would use cfls for the seedling stage as well

take the plastic off the cubes may help your roots breath ?

to me looks like nute burns or over water

do you have roots -no roots no food -just water if you use a heating pad cant just let it go to whatever temp it wants to -must get controller set to 78-80 deg

good luck -you need it

just looking at those seedlings makes me cringe- - growing from seed sucks there so pathetic and lame , check your ph ..bla bla ...good hard crusty cuttings is what you need =)

take em out of that room and give em some air for a while mabye a fan

Thanks for all the input everyone. Really appreciate it.

Things I forgot to mention:

The strain is Maxi autoflower by Grass-o-matic. This is the second batch that I have had with this strain. The first batch all seeds died except one. And so far the second doesnt look great. I am not blaming this on the seeds, however, I do have 3 freebies that I planted at the same time. These are looking MUCH better. They have slight leaf curling due to over watering, but other than that they look awesome. Strains are Rocklock, Sharksbreath, and Kandy Kush.



The only variable that I can think of that seperates the freebies, from the Maxi's is the heating pad (which I have removed). The freebies were sitting right on the edge of the heating pad, and I dont think there are coils there. The others were right in the middle, so they were getting the most heat. Someone mentioned maybe some good air movement. I do have a fan in the room circulating air, and I have an inline fan hooked to a carbon filter that runs into my light. This comes on for 15 mins once every hour. I do NOT have fresh air coming into the room...

So again, on your recommendations, I have:

Removed the heating pad (temps are at about 71F w/ light on, and about 65-68F w/ light off
Switched to regular water ph adjusted

Any other thoughts?