2ec is too much... you should probably back off before you add more.. .but plant dictates such things.. this is a generalization.
due to evaporation, ec should be higher over time, mathematically, physics, laws of physical world being proof... the plant's roots are not selective. it cannot pick and choose what fits through... it is either physically small enough or is not... any nutes for coco that aren't chelated and readily useable are the wrong nutes for coco. Sorry, roberts, but i gotta contradict you on that because it's not true what you said is occurring. don't take it personally if you read this like the last time. (though i was more of an ass last time, bwahahaha)
potential reasons with cause and effect...
some microbes are possibly eating it. There could be some sort of chemical reaction taking place and a precipitate forms or otherwise no longer a molecule that impacts EC. It doesn't disappear like a fart in the wind just cause EC dropped. they don't evaporate. they don't grow legs and walk off. (relative to resolution of this context and never grows legs, obviously)
So, i'd be a little concerned that the runoff is oddly lower. if the plant isn't showing deficiencies, that's great. you have some various symptoms present, but nothing crazy... rate of progression will tell you more than i can from a picture. (some twisting of new growth, maybe a bit thin too, not sure? maybe heat or light stress with the slight tacoing?) good thing is it's slow moving if it is something to worry about or not. I wouldn't feed more based on what i see. it's a lush plant as is.
Maybe, try a h2o2 drench? but then you have to re-inoculate with any microbes you added previously. lol, wonder if it is any of those products causing this... you don't need microbes as you do in soil.. i'm sure there may be some benefit, but the primare one is not relevant for coco/hydro nutes. your nutes are already chelated and ready for uptake and use.. maybe, try one put without the re-inoculation and see what happens with runoff after a h2o2 drench... 1-3% concentation is safe. go dilute some 3% 1:1 in next fertilization for one pot. try to keep all other factors the same.
if you are indeed feeding too high like i assume, you'll see a progression of issues in canopy over next 2-3 weeks... the plant is much more sensitive when growing buds compared to elongating stems and growing leaves. usually all i have to drop is 10-20ppm of N in flower to avoid overly lush leaves (too dark)... what ppl "boost" p/k to i feed from mature vege on, i'd wager... lol. if i add any more the plant burns. becaue i track ppm of of each molecule fed, i can say this with confidence.
check out my soilless ppm breakdown (it's usually 5-10% higher than what is listed in screenshot used in any diary)... use an online nutrient ppm calculator to resolve this better... learn the parts and the learning curve is drastically reduced, plus you can make adjustments with greater knowledge.. infer things more easily when you see multiple symptoms etc etc... thngs become cut-and-dry with zero difficulty in resolving what is actually going on because you know what you feed it. Environment and water used may have impacts on what works best for you. my tap is very hard.. so yu may need more Ca than i use. my mix works on 95% of plants with no tox/def symptoms of note before harvest is ready.
At this point i don't need to break my ppm down anymore... familiarity is enough once basics are hammered out / learned. Also, if you ever switch brands, you can do the math and adjust dose to match your previous ppm breakdown, or nearly match it... . and expect same results.
you should feed how the plant tells you to feed it... starting with a properly balanced 1.3-1.5 EC mix. you should fertilize every single irrigation in coco with 10-15% runoff.. this will ensure there is no buildup.. also will show that if the runoff continues to be lower in this context, that something else is definitely at the root of the loss of dissolved nutes. Wait for at least some dryback before fertilizing again... the 10-15% runoff eliminates possiblity of buildup. still have to worry about your root health, of course.
"boost" if you think that rhetoric is real... it's untested anecdotes from what i've seen so far. lots of confirmation bias/ego involving small samples and even sometimes overtly different methods used on plants for comparison (which makes comparison absolutely useless). i'm a fan of pushing limits, but "boosting" that involves major leaf damage i wouldn't bet any money on being beneficial. phtosynthesis is 10x weighted factor to results than simply providing nutes. nutes are 5% impact of the total picture. it's more a matter of not stepping on our own dicks than doing anything special or different. we can't play mad scientist and convert a pig to a princess. boosting is like putting lipstick on a pig... prolly should have been feeding the elevated levels before that point if it didn't cause any damage.
you can tell you are matching aplant's metabolism well if you do't have toxicities or deficiencies... overfeeding doesn't make it work faster or better.
Coco is best 2:1 or 70/30 perlite... sphagnum peat is better at 50/50 for a soilless grow (check out bugbee's maximizing yeild video on youtube). the difference is due to capacity to retain water... one holds quite a bit more than the other and it's all about proper drainage and more accessible o2 in root area. going beyond this will just increase rate of irrigations... which might be part of a larger plan, but on its own is not necessary or beneficial..
feeding on demand or frequently tends to have better results than 1 ever 3-5 days etc... but the dryback+drinking must allow it to be non-detrimental as far as overwatering or dangerous microbes growing on your roots -- if perpetually too wet. save yourself the experimentation.. someone has done it in a lab-precise environment. (watch a bunch of bugbee vids... devoid of nonsense and ego-drive dreck.. great source)
the fce light has fairly accurate spec sheet, so you probably have an accurately calculated DLI given area of coverage too. still use plant behaviour to fine-tune, if you only used math to start. just in case....