This is the first time I attempt to grow plants from seeds.

I've noticed about half of the seedlings aren't growing very well.
More disturbingly, greenish spots have appeared on the soil. It makes
me think some fungus has taken hold. I went back to the books that
I've been reading and realized that after germination the temperature
should be lowered, which I didn't do. Also, I failed to provide
ventilation, something which is generally recommended. So have made
some changes already to correct these errors.

My question is whether the symptoms I've described should lead me to
throw away the affected plants, or should I wait in hopes for a better
outcome now that I've made some basic changes and as long as the
seedlings are still alive (which they are). I'd hate to "over-react"
by dicarding plants that are still salvageable.

I'll appreciate any advice. Thanks!