92 is still too hot. Remember coco has no nutes in it too start with, are you giving the seedling everything it needs? Is it short in cal/mag? Ro water or distilled water would make some problems here too. You need a complete fertilizer for coco, any hydro ferts should do, if it is low in one thing your plants will show it. You could have over ferted but you were right to feed the plant from the start.
You need to read up on growing in coco as well, coco growers would be able to help more.