I brewed a summer ale this past Sunday and forgot to add the second half of the DME which I was planning on adding towards the end of the boil. So I added it right after flame-out and stirred until it dissolved in the wort. Should I be concerned?
Nope, no concerns at all with that. It was added while the wort was still plenty hot to kill off any nasties so you're good.
May be slightly more bitter.
Ok, I did figure it may be slightly more bitter but I'm ok with that. However, I did add 5lbs of pureed mangoes after flame-out while the wort was around 200F.