I’ve been a bit busy this past week with relatives in town and they’ve just left a few hours ago. Finally able to make a decent reply back.
I appreciate the tag in which you included me with some awesome growers here on this forum. Sad to say that I’m nowhere near their level of expertise in this great “hobby”. I’ve only got one grow under my belt and getting ready to harvest my Gelato gals any day now. But I will give it a go and try and give you some constructive criticism as best as I can. 
Swag - In my world it means: Scientific Wild Azzed Guess. Not to be confused with schwazzing which I’ve looked up and can’t figure out yet. All in due time.
That’s pretty much how I guesstimate and start counting the days to harvest. But ultimately checking trichomes will reveal the true time to harvest. Or get you close to knowing that the day is near. After reading lots of posts on that subject there are certain strains out there where the trichs will not amber enough to give an accurate time table of when to harvest. Gotta love the variables associated with growing the medicine.
Oh yeah… understandably so. My first harvest I had to chop them a week early because I found bud rot (low temps at night and RH too high) on a few of the colas. After being pruned, washed, dried and cured the end result was a heady buzz that had me a bit anxious slightly paranoid feeling. It’s been six months now and the buds have gotten much better and the high has evened out with the stone being much more euphoric and slight audible psychedelics noted. In essence I could hear music and sounds more readily and amplified. Knowing that it made the stone more pleasurable. A good head buzz also can sometimes make chores and projects go faster and easier. That’s why I’ve noticed some growers grow several different strains at the same time. That’s so they can have different highs during the day for what ails them. Just MHO though. 
I’d say that if you’re happy using Jack’s and like the easy peasy method of mixing then continue using it. Or, try another line of nutrients and give them a go and compare what you like and don’t like as compared to Jack’s line. I use Jack’s as do maybe half the growers on here do. At least the growers that I keep tabs on do. My first grow I used MG Organics and was able to grow some decent buds. Like most newbies I did overdo and push the amount of nutrients causing some deficiencies and burn. But I don’t believe the MG organic nutes were chelated to stop those problems from arising anyway.
I’m not familiar with Lost Coast and it’s effects. But I would be wary about using anything your last few weeks before harvesting unless you are having issues with the ladies being outside. I’m not gonna knock using it to you or anyone. Simply, I just haven’t used it. But will keep it in mind and could be something used and kept in the growing arsenal for future grows.
Looks like you’ve got the indoor space grow room ready for harvest. I concur with the other posters in that your temps aren’t much to worry about. But do keep an eye on the RH as you don’t want to have an environment conducive to mold. Search out the thread “Preparing to harvest” on this forum if you haven’t already done so. It has some really good info regarding the temps, RH and the curing process. Lots of good info nonetheless.
I’m sure you can harvest the buds as they mature to your liking and keep others on the plant to mature at a later date with no issues. I’ve read where some growers do that to keep the high consistent and get as much product as possible.
Btw clipping the tips off bad leaves is mostly esthetic. If it bothers you then give them ladies a trim. Nice gourds! At first I thought they were yellow squash. With yer latitude yellow squash may be done harvesting this time of the year.
Anyways, they’re still looking good. Eventually you’ll find out what works for you. Aquiring the knowledge to be succesful is half the battle. Applying it and getting the results you want is the other. Keep a daily eye on those trichomes. 
Peace 
