New Rust Spots

Check simple stuff like pH. looks like some components of substrate have nutes in it? you feed with a top dress that may have some 'slow-release' type ramifications even if not osmicoat or similar -- i.e. 100% does not go into solution on first irrigation etc... So, there's a whole lot of "maybes and i don't knows" here... anyone that gives a super confident response is just showing they don't actually know how this all jives - though there may be a good bet / high odds. rust spots without interveinal chlorosis could be Ca... could be locked out too by pH or another nute's concentration level.. just depends. Also, you have minor tip burn, so something is probably a bit high, but doesn't mean that it is locking anythign out with minor issues present. It is also nearing end of life, so some blemishes are almost inevitable. i'm not doing the math, but the concentration and ratios you mixed can be used to calculate ppm of each molecule given.. this would provide much needed insight as to what exactly is going wrong. if P is significantly higher than 50ppm, i'd wager it's lockout. it would also correlate to seeing some burnt tips. So... either a Ca deficiency with some other stuff slightly too high of less importance... OR it is because P is too high and causing issues with using Ca in the plant.. which results in the burnt tips coinciding with rust spots (and no interveinal chlorosis .. if present then Mg def/lockut enters realm of possibility too)... because of the way you feed (not a bad thing, just "is") some of this is a bit murky... but you can with familiarity and time guesstimate what it is providing on average. it would be worthwhile to put thought into that and it would make deducing what is going wrong easy... beware of "boosters" .. regardless the plant's metabolism can only handle X grams/day of any 1 molecule or even photons... force feeding it will only have negative impact pay attention to this stuff also helps hone a formula that causes the least amount of problems... soon enough you barely have to think about it... even forget how to fix problems cause they simply don't happen anymore... despite common beleive 80-90% of these plants will want the same damn things. other outcomes are due to improperly balanced formulas that some plants can handle and some cannot.. but a typical ego won't let that possibility enter frame of mind... nah, it's not "my" formula that could be off, it's the plants! lol.