Fill-out the troubleshooting form (copy-n-paste it here, and answer all the questions as best you can) The link is in my signature.

A couple of things you mentioned stick-out, but for an accurate diagnosis, we'll need all your info. But the topsoil is likely waaaay too 'rich' for seedlings, you can't ph runoff water with those color-coded test kits, adding nutrients or tea's to seedlings is a bad idea, (seedlings are too young and delicate for feeding)

Window grows rarely thrive. Varriable temperatures and neighbors can notice. Get 'em under lights, and keep them there. The daily changes in light intensity and spectrum freak plants out. Get a timer for the lights.

...But you really should fill-out the form...and read till your eyes bleed. I recommend you look in the closet growing section and read what others in your situation do for a healthy growroom.