Cheese grow week 4 bud help please!!

theese are my three big budda cheese plants just entered 4th week of bud. my plants as you can see from pics are what looks like burning on the tip of the leave and some yellowing on some other leaves. What can cause this ? im using a 600w light with nutrients coca a+b pk13/14 boost and cannazym ??Any advice or tips would be much appriciated thanks

Anybody out there .......?

Doesn't look too bad, you most likely overfed it a little bit and its too hot in your tent
it looks like it could do with spreading open too its quite bushy at the bottom
you could cut back on the food it has very fine sativa leaves often they need less food or they can burn
when other plants do not burn on the same EC i have burnt sativas on 1.1 to 1.3 EC i just let them grow it out
get more air circulation in there

peace

Ok thank you very much for your advice could you please tell me more about spreading my plants open please never done this before so could do with a little more advice thanks

Tying down the main stalk so as the lower part of the plant gets more light.
Search for LST.
Monster cropping is a option as well.
Study!!