Darkrai: darkrai without nigthmare? no way replace foul play for nightmare. Also dream eater instead of nastu plot would be considerabe, since it covers fighting, which few of your pokemon do.
Tyrannitar: an earthquake would be a good idea, even stone edge would be good. Have crunch, earthquake, stone edge and areal ace/superpower/dragon claw/ dragon dance.
Sharpedo: don't know much about sharpedo, but looks good to me. (or is crunch better than night slash?)
Krookodile: don't know much about krookodile, but looks good to me.
Umbreon: i agree with MrKijani