Did I miss an area or something?

I’ve been doing a Hard Mode Nuzlocke Run of this game. I made it to Suntouched City, and the Level Cap for the Gym Leader is 25! Since it’s a Nuzlocke Run, I feel that most of my Pokemon should be at or close to the Level Cap in order to stand a chance against the Gym Leader. However, the Level Cap right before Cyan Cavern was 19. By the time I made it through Cyan Cavern and I fought the Gym Trainers my Pokemon were Level 20-21.

Is there an area somewhere that I missed where I can fight more stuff to level up? Or am I just expected to train against Wild Level 16/17 stuff for a few hours to raise my team’s levels?

Go to the Broadcast tower and do the first two missions – I’m not gonna spoil anything, but the second available mon will be very helpful

I already did that. Is the D.Grimer really that good right now though? It has Sand Tomb/Swallow/Spit Up/Minimize. Is Sand Tomb enough to carry me through the Gym in Hard Mode?

Lvling til you get to mechi town is difficult. You just really need to be patient in cyan cavern.

it learns bulldoze at level 26