I can only curl 25lb dumbbell!!?

I am 17 years old, 6feet 2inches tall and weigh 155 lb.I can do 3sets of bicep curls(10 reps each) with two 25 lb dumbbell(2x 25 lb dumbells using them at the same time).However,I cannot do more than 1 rep of bicep curls with a 30lb dumbbell(2x 30 lb dumbells again...).I am greatly saddened by this because I want to be physically strong.Please help me with some advice.Thank you.