Do you roam or recall more often than the enemy support? Do you leave the lane to ward at the wrong times, so that you lose too much xp when a big minion wave is cleared?
I see you play a lot of Vel'koz and Fiddlesticks. I know from experience that it's easy to lose xp as Fiddlesticks if you cause the waves to push forward and then sit back too far or get zoned away from the waves. Also if you damage an enemy wave with some poke, but don't fully reset the wave, you might accidentally start a slow push towards the enemy which can cause you to lose a lot of xp. If you aren't intentionally starting a slow push to setup for a dive or to take a turret, then you will probably want to shove hard and reset waves frequently with your champion picks. I know from playing a lot of Fiddlesticks support that spamming E poke will pretty inevitably push the lane, so I find it's best to just play aggressively and keep your minions shoved into the enemy turret while tracking the enemy jungler and mid laner via the minimap.
This is usually difficult for the enemy laners to retaliate against on their own and leaves you in a position to reset the wave if you feel the enemy mid or jungler are coming to gank you. If the enemy mid or jungler come, then you need to stop poking with E and let the wave reset towards your turret so that you and your partner can back up to a safer position without getting zoned from a ton of xp. Also communicate with your partner and ping danger when you see the enemies mia or the gank coming and ping them away from the enemy turret so that they stop pushing and let the wave reset too. If the enemy mid and jungler spend a lot of time in your lane to respond to your pressure, your opponents will hopefully lose levels due to xp sharing. Hopefully, it will also help your allies win their lanes by getting the enemies to camp you. If the enemy team doesn't camp you, then take the bottom lane turret early with your aggressive pushing and then you may want to go to mid lane early.
I don't play a ton of ranked, but I have gotten to gold with Fiddlesticks support, so I hope this advice is useful to you if that's your goal.