Is this ph issue or ppm ?

Did you check your pH meter ? Often happens it goes out of range, so a frequent calibration is needed...

In coco you need to use extra CalMag. The ionic bond in the coco will pull magnesium and bind it. In order to prevent this, people typically will wash their coco in a CalMag product to fill all the ionic bonds in coco. Then it’s smooth sailing. I suggest mixing up more CalMag in your solution. Also, what I would do immediately is to flush out your plants with enough water to get nearly half of it to run out the bottom. Your water should be pH balanced at 6.3 and then add CalMag to this as well. People often times take the plants to the sink so everything goes right down the drain. Hope this helps.

If you want to attempt to guess at nute lockout issues, "Mulder's Chart" is an attempt to show all the interactions.. what locks what out - it's not always both ways. Some stuff actually have a stimulative effect on other elements... higher N needs some proportion higher Mg, for example. I'm not goingn to guess how much but the relationship has been shown in plants. They mostly function in similar ways so this is applicable but think of it in more of a general sense... it'll help more when you do 'something' and see symptoms of related elements, while keeping other factors relatively the same. e.g. you add some N to formula and a week or two later you see mg issues.. this is a bad example becaue Mg takes 5 weeks from inception to show symptoms.. so you'd want to look back 30-35 days in regard to Mg ppm of fertlizer given. again, assumes soilles context. 'hydroponics' nutes used.

is your pH off? This is question you can only answer by measuring it one way or another.. do note that runoff pH is not exactly what it is in the substrate. Compare to what you put in and that will help interpret it. Soil slurries have drawbacks of their own.. being consistent abouit how wet it is, where you take it from, when you take it relative to last irrigation can all help make more sense of it by eliminating things that cause it to swing naturally. Same with runoff.. if you measure right when it starts, it's going to be more inaccurate than if you measure toward middle or end of runoff. Runoff pH makes more sense if you have a baseline from "good" times when nothing is going wrong that you can compare to, but if it is drastically alkaline or acidic, the answer is obvious either way. the fact these symptoms seem to very and more than one presenting, pH issues are definitely a potential reason for that.. so is nute-lockout if feeding - 1 or more of NPKCaMgS is too high it will cause availability issues of other nutes. this is a soilless contxt... review how you have fertilized.. if you were a lot higher than 1.5EC for a prolonged period of time, you likely overfed. That won't rule out if 1 type of nute was too high while overall EC remained in a safe level. (that's nutrient EC not incuding anything your tap water adds... can calculate this from your labels and an online ppm calculator or i'm certain there is an app for that too) Don't let something like this progress so far next time. It is good to be patient and make sure the symptoms clearly displayed and easily diagnosed with a lef chart before reacting, but this is too long. It is easier to add than take away what was mistakenly (in hindsight) added that is now compounding any previous problem. if all this damage happened overnight (or very fast), that's gonna back up the ph/lockout possibility. the tip-in fade is typical of N-def but should start at bottom and move up on the plant. K-def often causes damage in the serated tips along edges of leaf, then some interveinal chlorosis and spots as it progresses. chlorosis (paling) in new growth accompanies this. p-tox can have a slightly different tip/margin burn effect than K-def, but similar.. but p-tox will be more pronounced in tip of leaf than around perimeter. chlorosis in new groth, but no interveinal chlorosis like k-def. get a leaf symptom chart off google image search. Reference it.. learn it. The one with cervantes name on it also explains mobile vs immobile etc.. this is the one i prefer. https://duckduckgo.com/?t=ffab&q=marijuana+leaf+symptom+chart+cervantes&iax=images&ia=images -- first one i see at top by 420magazine.. but look for highest resolution of that version you can get. That way you can zoom in on any 1 symptom example with good reso.

Check Runoff first, flush with tap or RO with calmag for a couple of days then start feeding low-strength nutrients. too much ppm could lead to tip burn but too high or low pH can cause it also. Check Liebigs'barrel theory