Leaves are curling on some plants...

I saw in a thread on leaves that said if they curl or roll the sides that they may need feeding...So on the 12th I gave them a of 1/4 strength SH nutes. I was worried because they are different sizes even though they were all planted together, and I didnt want to burn the smaller ones. The smaller 4 are looking great to me but the 2 biggest are curl. Could they be telling me they need a little more than the others?



These are the biggest that are curling




This a pic of the others

how is the humidity in your room?