Hi and welcome to UU! :)
Shuckle's only problems that I can see so far is that 1: Run Rest over Run Rest SR (I'll explain why later) And 2: Run this EV spread: 252 HP / 196 Def / 60 SDef
With this, you can basically tank any move and Rest up. Or maybe, if you really wanted, you can use Infestation > Encore and that way when they're trapped, hit them with a toxic :)
Your team is very weak to Ghost type moves, and with LO Bisharp being a sweeper, not a tanker, it can hardly switch repeatedly in on a Shadow Ball/Claw. So instead of Scarf Chandy (not being fast in the first place) Try using Arcanine or friends. This way, you'll lessen the ghost weakness while keeping the Flash Fire and Arcanine is faster anyway, also, you're lakcing physical attacker so Arcanine also fills that spot.
Blastoise is good, however, run Aura Sphere > Dragon Pulse. This way, you can hit pesky Umbreons and Dragon Pulse provides no coverage that Ice beam can't handle.
Now the reason I got rid of rocks on Shuckle was so that Celebi can run it. There is absoutely no reason to run a special attacking celebi with T-Wave. Instead, run a Heal Bell support set with Stealth Rocks. This would mean a moveset like:
252 HP / 60 Speed / Either 196 Defense or Special Defense.
Some problems with Bisharp. Why do you have Dark Pulse? Replace it with Iron Head.
Also change either Pursuit for Knock Off, or Dual Chop for Knock off. Also, not really needed but maybe have Brick Break in there for Chansey's.
Latias in my opinion can't really sweep anymore, with Florges running around in UU, which is why I'm suggesting another defensive set. Either go defensive or specially defensive, opposite of what you chose for celebi. Then run a moveset somewhat along the lines of:
Wish, Protect, Defog, and Dragon Pulse/Psyshock.
This way, you'll have Wish Support as well as defog support. However, if you don't like the defog support, run Rapid SPin on Blastoise and have Toxic here instead.
Good luck with your team!