I used langbeinite for the first time this year. I got it after planting and side dressed it but I am sure it helped. I am going after a lot of edible greens, spinach included. I have a bunch of peas in waiting. Have you started seeding indoors yet?
I’ve been using it for 3-4 years now. It’s potent stuff and keeps it organic/natural. For everything slightly acidic it’s a must add amendment, IMO, because of the sulfur and high potassium. Tomatoes love this stuff.
I won’t do indoor seedlings for fall. I simply direct sow all my stuff in Aug/Sep inside a greenhouse. It’ll be large sized by Xmas and survive until July. Lettuce, kale, mustards, peas, & onions. I can also just randomly toss the seeds around like a drunk instead of have to tend seedlings indoors for 6-8 weeks.
I do need to get out and amend/water the 3 greenhouse beds but I still got purple kale in 1 bed in there and pulled a nice onion yesterday. Also removing hornets nests that are too large in the doorways. I’m adding like a wheelbarrow of compost/manure to top them off, a few pounds of dry amendments and then direct sow.