I've got some pretty bad news for you, I'm afraid.. the second picture, the fifth and sixth and the last picture all show signs of bud rot... if you can grab those dead leaves and pull them out easily, it is DEFINITELY bud rot - but I wouldn't do it when the plant is anywhere NEAR the other one that does not have those dark patches. If it is bud rot, the spores will travel without you even seeing them. You don't have a diary so there are no more pictures for me to look at - but I'd like to see a picture of the whole plant... it may be that you're going to have to dispose of the whole thing as the rot looks like it's really taken over the plant.
Look up the fungus botrytis in cannabis - how to identify it, how to deal with it ... THIS is what I'm afraid you're dealing with. So far, the other pictures (are they the same plant?) look ok but expect to start seeing bud rot develop on that one as well... And please, start a diary so that when issues/problems/concerns come up, we'll have as much information as possible - it will help us help you!
Good luck -