Hey nice looking spike stacking team
Looking at your team i see that you are quite rain weak which is kind of ironic seeing as your team has its very own Politoed to supply rain for your opponent. With rain supplied a Sub+Dragon Dance Gyarados tears your team apart being able to avoid status moves from your team using Substitute while being able to boost its speed with Dragon Dance and threaten your team with its stab Waterfall that is further boosted by the rain your team supplies. Your best bet is to get Cofagrigus in to haze it and even then it doesnt want to eat two boosted Waterfalls. Breloom isnt safe either getting destoryed by Gyarados's Bounce. Even the offensive varaints of Gyarados are an issue at +1 they can outspeed your whole team and continue to pick up Moxie boosts although it is harder for offensive Gyara t set up if it does make it to +1 your team is going to be in trouble. Kingdra works very similarily to Gyarados being able to threaten your team once it starts using Dragon Dance however Kingdra has Swift Swim doubling its speed in your rain. Starmie is also quite a big rain threat when Cofagrigous goes in to spinblock it won't like taking a rain boosted Hydro Pump not to mention he can outspeed your whole team except Politoed who all three of his attacking moves are not very effective against Starmie. With Thunder(bolt)/Ice Beam/Hydro Pump Starmie can do some real damage to this team hitting three of your pokes super effectivly if Cogagrigous is out of the picture Starmie can also spin your valuable hazards. To help remedy your problem to rain offense i suggest Ferrothorn>Jirachi Ferrothorn still retains Jirachi's steel typing but also has a secondary grass typing helping him against rain teams alot. Much like Jirachis Wish support Ferrothorn has Leech Seed to keep your team healthy while he can also run Thunder to paralyze apoosing pokemon like Swift Swim Kingdra who gives you trouble. His Powerwhip also helps him against Starmie and he can take a bit of pressure of Deoxys-D setting up all the hazards as Ferrothorn can run Stealth Rock. However if you feel that Stealth Rock or Thunderwave arnt good options for Ferrothorn then you can run Gyro Ball if your not using Thunder Wave or Protect. If you are running Stealth Rock on Ferrothorn Deoxys will probally be wanting Recover instead. I reccomend you try all these options to find out the best one that quits your team.
Ferrothorn helps you alot agains Kingdra and Starmie and just water-type moves in generall because your Breloom and Politoed cant really take alot of rain moves due to them having no recovery and defensive ev spread. However Ferrothorn cant really take on Sub+Dragons Dance varaints of Gyarados as they eventaully take out Ferrothorn and Ferrothorn can't stop them from setting up. A good suggestion would be Hidden Power [Electric]>Focus Blast On Politoed. Hidden Power [Electric] murders Gyarados and also gives Politoed a move that is super effective on Starmie which is also nice. Focus Blast may be good but you need the super effective hit on Gyarados and Landorus and Breloom both have Fighting-Type moves so you can still beat Ferrothorn pretty easily.
good luck with the team i hope i helped!