"of 63/70 days" -- get that out of your head. What the breeder says is a ballpark figure at best and can help you choose the right strain for your timeframe, but don't even use those numbers as you grow, though. Once you plant it.. you simply react. There is no pre-ordained time limit. That number is very likely inaccurate so just pretend it doesn't exist. Many breedres happily lie about such things to sell more seed.
Visible signs that point toward k-deficiency and Ca deficiency... Spme signs of over-feeding, so is it an actual physical deficiency or lockout?
Diagnosing based on visible symptoms is not discrete. More than one thing can cause most symptoms.
Keeping track of what you provide over time (entire time, not just last night or last week) and being familiar with your soil and products used can fill in the gaps for a much better diagnosis.
e.g. if oyu know it's getting plenty of Ca from what you provide, that points toward lockout being more likely.
Without familiarity, might be safest to go with water-only for a few irrigations and see how it reacts. if the rust spots get worse, probably is a Ca deficiency. If the damage around the serated tips gets worse, probably is a k-deficiency, too. If the negative trends slow at all, then lockout becomes more likely... deductive reasoning...
Always safer to take away than to add more -- adding "more" when a deficiency isn't the problem will only make things worse
good to take notes on fertilization over time. When you have a better idea of what is happening hear through trial and error explained, you can look back several weeks or even months and adjust your fertilization to avoid these problems in the future. Be systematic, or you'll forever be running around like a chicken with its head cut off.