Wow, this forum's been around FOREVER haha. Anyways, I've been having this problem for a month, and alot of the answers on here didn't really help the original poster, as they just addressed 'clone death' in general.
This is specifically about the 'tops', or those 2 tiny new leaves, the ones you don't cut the ends off of, browning and dying.
At this stage your original 2 big leaves stay green for a while, and if you don't know about cannabis, you might still 'have hope', but, since there is no way for new growth to occur at this point, it's only a matter of time before the rest of the clone dies.
FaCultGen nailed it, without explanation of why, but I realized the issue I'm having is exactly because I'm using Wilson rooting gel.
Key fact for you all to keep in mind: rooting gel is a superior product over powder, a bit, HOWEVER, it contaminates easier than powder!
When I started cloning a few years ago, I had 95-100% success, and I only ever used Stimroot powder #1. I was having success with the gel, but I just realized the decline has been 'over time'. Each time I've cut clones, I brought them downstairs, usually 20-25, set things up like an 'assembly line', poured some Wilson rooting gel into the cap(DO NOT DO THIS lol), and well, I left the container open and exposed while I worked! One time, I left it open all night by accident, even though I closed the box flap. I now see the extreme err of my ways haha.
So, gel is technically a bit better than powder, because it's easier to get a full, lasting coat over the stem cut area. That being said, I now see it as only useful for amateurs. Every 'pro' I've seen take clones, always used the Stimroot powder. Why? because they know how to use it, and they have nearly 100% success rates, so why change it? It's not that these 'pros' are cheap either, as it's only like an extra $2 for the gel. Therefore, I'm immediately switching back to the powder, I have like 5 bottles I got free hahaha.
My advice to any general cloners who stumbled on this thread. Most of the advice folks gave is actually all useful, but no only FaCultGen addressed the specific issue. The browning of the tiny 'tops' is caused by infection at the stem's cut point. This can also happen from unsterilized scissors, so be sure to use clean scissors also! I would take most of the above advice however. As for how to use Stimroot powder(or any rooting hormone powder product), Dump some into a small plate, add just enough water to make it easier to stick to the stem. Immediately cap your Stimroot container. The powders can be contaminated, just not as quickly or easily as the gels, but better safe than sorry. Make your 45 degree angle cut(I always make a 2nd cut, not just when you cut off of the plant, this ensures that no air can be trapped, and avoids any infection that may have occurred during the time you took your cuttings from veg room to wherever you're doing your planting). Rub as much powder/water onto the stem cut area, and about 1/3 to 1/2 an inch up(roots sometimes will grow out the sides of stem also, why restrict them). plant into your medium. That's it!
If you choose to use a gel, that's fine, but that step of putting the cap back on immediately, is far more important step. Also, I now wonder if after a few months after opening a bottle of gel, if you should just toss and buy a new one. Meanwhile, the powders, if respected, will last YEARS.
Final tip: It's summer here in eastern Canada, but temps rarely go higher than 27C/80F. 80F has been the normal temperature in my cloning room though. That being said, I took 7 prime clones from my new Gelato seedling plant, and decided to use a heating pad under dome, even though temps were already high. I just noticed 6 out of 7 have rooted in my new shattering personal record of 8 days! I don't know which things worked(clearly the heating pad was main reason), but I only left the air tabs 100% closed for first 48 hours, then opened them a quarter or so. People have recommended misting clones and not watering your medium(rockwool/pucks). I've never done that, I water the medium once it is getting dry. If you use a heating pad, especially during already warm conditions, you will need to water the cubes/pucks EVERY 2 days. If you miss that by a day, they will die very quick. If you do everything I just said, you might have rooted clones in just 8 days instead of the typical 14 days.
Cheers.
EDIT: Upon reading a bit more on rooting gels, I wouldn't recommend them at all. The gel can coat the stem cutting area TOO well, and block oxygen, leading to no rooting, root rot, etc. I've never had that specific issue, although it's possible it's slowed down rooting, who knows.
