[GAMEPLAY] Illaoi VS Trundle

So basically top me vs , around 8 minutes we both had ultimate and we engaged in a 1v1, after pulling his spirit and ulting i had about 3 tentacles busting down on him and his spirit, however he ulted me around the beginning of the fight and for the first swing of all my tentacles no damage was inflicted. Now I'm not talking about he was tanky enough and taking enough health back to negate the dmg (as one could not against an illoai burst with 3 tentacles and beating down on not just the spirit but the champ too) but his health bar did not move down at all or showed any signs of going down and back up from healing. So basically my initial dmg was completely ignored and this scenario played about 2 more times in the match, I wish i was recording but if anyone could help test this and find any more info on it that'd be awesome, I just want to make sure im not crazy mostly.