You just wind burned them a little bit, I would guess. Considering that your plant IS just getting out of the seedling stage, was the fan blowing across the top of the pinapple chunk? If it was at all causing the plant its self to shake then I would guess that the bigger fan burned up the plant by wicking moisture first from the leaves, and then ripping up a lot of your tiny roots. Switching to the smaller fan should help, but if you still want to use the larger fan I would suggest moving it out of the direct path of foliage and somewhere else in the room if you REALLY needed the added circulation. Based off of the pic with the fan pointed at the plant I would say wind burn. Wait until you have at least 12 points of growth on a plant before adding direct airflow to the plant matter itself, and even then monitor your plant. If you wait until a few of those internodes have growing tops it's good indication that the roots are strong enough that you won't tear them through the excess wind. When you add too much wind to a plant that size you have to remember that the tap root doesn't branch very much until the cotyledon leaves fall off, so it acts like an umbrella in the wind, it just wants to lift off and tear all the hair sized roots it has started to form. IF I WERE IN YOUR POSITION I would move the fan so that it just circulates air, and I would foliar feed with a very mild water and molasses foliar feed. It will hydrate the foliage, and provide vital nutrients and sugars for your plant to recover. The plant above often reflects the plant below, and the damage that I see indicates problems with the roots, hence why people are suggesting ph and possibly the PPM of your water. Make sure that your ph and ppm are all within normal range too! All this is with the assumption that you purchased a soil the would "feed for blank months" which are fine for the first month of growth if you know what you're doing. All my best vibes go to you and your plant friend!
