i have 7 plants,they are all 17 days old,they range from 7-10 inches ,i looked at many outher plants online that are are the same age and they all have more leaves,and there leaves are bigger,my plants are just began to sprout there 2nd set of (true leaves).and there first set of true leaves are only about a little less than a inch long.is this normal?any idea what might be causing this?thanks