yellow tip leaf

Hi guys, first time growing a plant can someone please tell me if I should start LST at this stage? Plant is 31 days old . Also noticed some yellow on the tips should I be concerned? Thanks in advance :)

Hi there, I am growing a Pineapple Express (Sativa Dom) and it’s at day 6 from germination at first they were growing fine but when the first true leaves grew in I noticed that the side of one of the leaf blades was turning yellow and one of the new growth leaves is also yellowing at the tip...