I'm a lee sin otp, and I find it very difficult to fight against tanky comps, but I don't know what other jungler to play against a tanky comp. Since I play Kha, lee, rengar if i see anything remotely tanky I get pretty scared. Any good Junglers against tanks?
Jarvan can do max hp damage and has armor shredding. Maybe give him a shot?
beast. or 
disgusting overpowered underturret killing salt generator for enemy
Kayn is an extremely fun champion and one of his forms is basically designed to screw over tanks. The more hp they have, the more damage Rhaast does and the more he heals, which also allows him to heal off tanks while simultaneously landing aoe to kill carries. If you like Rhaast enough, you can also learn Shadow Kayn who is an absolute blast to play as an assassin. If the enemy picks tanks, Kayn can counter them. If they pick too many squishy damage champions, Kayn can also counter them. There's very few champions who counter both Kayn forms so he is almost always a useful pick.
Some other fun options are as follows: Nunu is extremely fun if you wanted to counter their tanking by tanking yourself and frontlining for your team. Kindred, although very weird to learn compared to any other jungler, scales harder than most bot lane ADCs and obliterates the enemy when fed. Rek'sai is a diver kind of like Lee Sin and is pretty nuts right now if you wanted to OP abuse. J4 is also a really good diver but I don't play him so can't offer advice there, I just know he is super tanky while doing dumb levels of burst.
Jarvan is really bad into tanks tbh. He can't deal with them alone, J4 is great squishy buster and his catch potential is top notch but he straight up loses in teamfights vs Sejuani, Gragas etc. If you want a good jungle tankbuster Trundle is a nice pick for that, Urgot jungle is good IF you don't mind having 0 pressure until 6. Also if you have the luxury of picking into Zac just pick Gragas or Seju and bodyblock his every E with seju Q or Gragas E
