It does look like damping off, but you mentioned two other components that would/may have caused problems without the damping off.
OF is hot for seedlings. I'm still using some Fox Farm stuff I was already sitting on (not
OF on seedlings), but the inconsistent results for seedlings in Fox Farm mixes, has convinced me to move to pro-mix for my seedlings, at least. But, without regard to the brand, we would like to start our seedlings in a non-ferted, pH buffered mix, preferably
not peat based.
You're not monitoring your water pH. You are using a pre-buffered mix (good idea, imo) but we also have to monitor the water pH so that when we water, we don't undo the buffered pH of the soil mix.
Yes, it looks like damping off... but, it could be nute burn or pH issues as well.
Please slow down a little bit, brother, and get these other things sorted out before you get too much further along.
We don't need to have you dying all over the place around here, every time we turn around! :buds: