Light burn or deficiency???

Hi guys I am currently in week 3 of flower and my babies are a lil taller than I would have liked... I am startin to notice these yellow signs at the top of my plants?? Isit light burn or something else? Also I have burnt tinged on other leaves towards the middle of plant. Looks like nute burn but my solution isn't even that strong??? It's at 1.6 ec. I am growing in soil FYI. I am told by my local shop to add calmag?? What does everyone think?

Thanks guys I hope u can help me out?

calmag plus, ph 6.5, check light distance

Lock out . And what he said ^^^^^

Check out your runoff pH. As said, this could be lockout due to pH being out of line. Know your pH before you add the water, then see what it is on runoff, should be around 6.5. That may be confusing- add water that is about 6.5 on the pH scale, and see what the runoff is. I'm in hydro but have had mothers in particular (over 1 year old) that have gotten all the nutrients they needed, and had deficiency. Low and behold, the pH was around 4.5! Even a pH of 5.5 is low for cal-mag absorption.

Def and nuts burn not so bad how much ec you give (nutes)

Check out the pictures for potassium deficiency in this guide

https://www.icmag.com/ic/showthread.php?t=231387

That's what it looks like to me. pH is probably the root cause?