Deficiencies? Nute burn? Help!

Hello everyone. First post on here for me, but i ussually use this site as my go to for info. I seem to be having some trouble with my plants, they're showing some kind of deficiency on the leaves. I use a substrate that already has perlite mixed in it... i live in a country where weed is decriminalized but still not legal so it's hard get my hands on some nutients that are made specifically for canabis so i tend to just use stuff i find in my local plant shop and have had pretty decent results untill now. Can anyone tell me what this could be? Its seems to only be affecting the plants of a certain strain. Although today i say some very small dots of rust on another strain aswell but might not be related. Anyway, ill attach a few pics and hopefully someone can help me out!

Pura vida

Probably a K and Mg deficiency. You usually can find a regular plant nute or nutes that together give a good npk ratio and all micronutrients. If you need help just post details on what you can buy (labels, content list) and maybe we can help you get the best nutes for the plants.
Also, tell us what you are feeding now. Seeing what it contains may help us figure your situation better.

Welcome to IC (plant Urgent Care!)!!
Here's a guide, possibly to help diagnose. Good luck!

It's rather early for such K signs. Following other metal spotting, I'm leaning towards toxicity.

My rule is 'if in doubt, rinse it out' using something known to be effective.

What are you actually using? Maybe we can spot an excess on the label or have some experience with it.

You can buy granular plant food for canna or even mix your own from supplies suited to plants in general. Maybe that is your real answer. Though tomato feed can certainly work.

It's a lack of calcium .

Calcium can go that far? I can see it's high on the list. Some pics show nothing else. That's pretty chronic for a single problem though.

In the replies I'm seeing Ca Mg and K being spoke of. All 3 of the main competitors for space on the medium.

I'm open to the idea it's just Ca. Especially as you seem so certain.

Ultimately a proper feed is needed. Tomato stuff would usually have more Ca than typical plant foods though. I have been through crops using Tomorite