Seedling canoeing leaves

Anyone know what might the problem here, if there is one.

Not sure of the strain. I have a 250w HPS about 5' above, still using a dome. Temp is about 85F. I'm just using PH'd water on the cube.

Did you PH adjust the cubes before you used them? Since you mentioned that you haven't given them anything but PH'ed water, that's the only thing i can think of that could be the problem.

I see a lot of salt build up in your dome. clean that shit out imo

And I think it's heat.

If you are using a dome you are cooking them. After they sprout do not use the dome unless they are clones.

Thanks for the replies.

Yeah I soaked the cubes in 6.0 ph'd water for 24+ hours, and I use 5.5 when I need to re-water.

The salt is from water used to humidify the dome. Yeah perhaps I should clean it out, but it's pretty benign if it's just sitting there, or am I wrong about that?

Last time I took off the dome with seedlings this young, they dried up pretty quick, which is why I'm fairly reluctant to do the same again. The temp isn't too high, but I understand it isn't optimal. I don't have many opportunities to check on it every day, but I suppose i'll have to if I need to give it some fresh air.