I have this card 3 star blue Gunner leveled up to MAX 50 and the special skill did not go past 5 I tried to add to the max level but it does not work so I got a max ed out hero that does not go past the 5th special skill level
Keep trying. Advice in the future is to use common heroes to max specials before using rarer ones or trainers to max levels.
When I am leveling a new hero without a super pressing need for it, I always do the low level color based training. It’s expensive and lengthy, but the worst result has been a 7/8 special by the time they get to level 50. And that happened exactly once, and was resolved on a 10X1* same color (20% chance) try shortly after. In most cases the special is 8/8 by the time I am tier 3 level 20 or 30 on a 3*.
You can try and do the same for special - 10X2* blues will give you a 40% chance. It will take a day to get the 10 via training because you’ll need to train 20 or so to get the 10, 8500 meat per and a backpack/sword so it;s not exactly cost efficient, but it’s worked well for me because I always have way too much meat these days.
It can be WICKED frustrating and the odds can feel like they are against you at times in this game, but keep plugging. Personally I wouldn’t sweat it until you have nothing better to do (my scenario above was I happened to have a bunch of green 1* cards from farming so I said what the hell).