Fantastic progress.
I am a big believer in solving tactical puzzles, especially at your rating level. I thought I had done well to attempt 20,000 of them!
Tactics, calculation and pattern recognition really is the single best thing you can do at your rating level.
I'd start to layer in endgame exercises into your study routine, in particular, Rook endgames and King and Pawn endgames specifically, and then introduce yourself to the topic of pawn structures/weaknesses. It seems like when ever I play someone around 1200-1600, if I don't beat them quickly via tactics, it's usually through an easy endgame as a result of pawn weaknesses in the opponents position that present easy targets for me to pick off.
Also, losses after a peak is extremely common. I tend to think of it this way, when you eventually climb to say 1300. This is you at your best ever. The other 1300s you're paired again are likely seasoned and established at that rating level and some are even 1400s-1500s on a slump.
So it's easy to be matched in rating but outmatched in experience. You'll eventually sustain the rating and climb further if you keep studying! Good luck!
2400 Puzzle Rating
My longest winning streaks here was 17 when i was at your level...it started when i decided to think very carefully on all the moves and not 99% of them...
I still remember the game that i lost to break that streak because i was clearly winning in the endgame and i decided not to think and just play by intuition one of my rook and i lost that rook...lol....
Good luck!
My best win streak is 9 same as you. I guess that was a while back, it is harder to get a winning streak going against better players.
40,000 puzzles! You need the chess addict treatment! 
No, just kidding. Good job, I guess? ...
Started my chess journey in January of this year. In that time, I've achieved a 1200 rating up from 373 at my lowest and worked my puzzle rating up to 2400. Seriously have gone kind of crazy with the puzzles. I've done almost 40,000 of them 😐. But I've learned a lot and I am still learning. I'm honestly amazed at how much information I've been able to retain and yet it's only the very beginning. I haven't even scraped the surface of the things I'm going to need to learn if I wish to achieve my ultimate goal of 2000 someday.
I've also met some really cool people, a few who have become good friends of mine. Never a bad thing.
All in all, I'm glad I rediscovered chess. It's been really good for me.
Good vibes to you all. 🙏
And out of curiosity I'm asking what your longest winning and losing streaks have been. For me it's 9 wins and 10 losses. The latter of which I experienced very recently and knocked me from potentially breaking through to 1300 all the way back to 1200. It was quite humbling.
Congratulations! By the way you probably don't need much better skill at solving puzzles in order to reach 2000 as I am 1900 rapid and my puzzle rating is 2200, although it is true that I haven't solved any puzzle in a year. The next step is to be able to spot some of those puzzles in games. I have just played a game where a 2100 missed an elementary tactic that you and I would immediately solve if it were a puzzle and yet, in the actual game, I missed the tactic for 1 move, but thankfully my opponent did nothing about it so I played it on the next move. Here is the position, you can treat it like a puzzle and you will probably solve it immediately. It is white to play. In the game I played Rd1, because I hadn't spotted the tactic yet, but my opponent played c6 (which does nothing about my tactic, it doesn't prevent it) and then I finally spotted it.
Here is the game https://www.chess.com/game/live/56257492013
Bishop x f7 is not hard to see...
It's a puzzle for a level 1400 Elo.
In a fast game and when you do not know that there is a puzzle that is not obvious of course.
From the chess rating comparison website
A puzzle rating of 2400 would equal 1424 to 1792 in Rapid.
My puzzle rating is 2505 which would equal 1482 to 1850 in rapid. My actual rapid is 1694.
Bishop x f7 is not hard to see...
It's a puzzle for a level 1400 Elo.
In a fast game and when you do not know that there is a puzzle that is not obvious of course.
It is an easy puzzle problem but in the game my 2100 rated opponent allowed this tactic twice and I didn't see it the first time, the second time I did see it and I played it. It was a 15+10 game. Sometimes positions that you would solve in less than 10 seconds if they were in a puzzle, you don't solve (you don't play the best move) if you get them in your games.
Bishop x f7 is not hard to see...
It's a puzzle for a level 1400 Elo.
In a fast game and when you do not know that there is a puzzle that is not obvious of course.
It is an easy puzzle problem but in the game my 2100 rated opponent allowed this tactic twice and I didn't see it the first time, the second time I did see it and I played it. It was a 15+10 game. Sometimes positions that you would solve in less than 10 seconds if they were in a puzzle, you don't solve (you don't play the best move) if you get them in your games.
I looked at the game and this guy play way too fast...less than 8 sec for that move and he still had 15:48 left after 9 moves and you 11:38
He write on his page that one of the key is to think very carefully on each moves but he only did it a few time after his blunder 
He is really strong though!
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Started my chess journey in January of this year. In that time, I've achieved a 1200 rating up from 373 at my lowest and worked my puzzle rating up to 2400. Seriously have gone kind of crazy with the puzzles. I've done almost 40,000 of them 😐. But I've learned a lot and I am still learning. I'm honestly amazed at how much information I've been able to retain and yet it's only the very beginning. I haven't even scraped the surface of the things I'm going to need to learn if I wish to achieve my ultimate goal of 2000 someday.
I've also met some really cool people, a few who have become good friends of mine. Never a bad thing.
All in all, I'm glad I rediscovered chess. It's been really good for me.
Good vibes to you all. 🙏
And out of curiosity I'm asking what your longest winning and losing streaks have been. For me it's 9 wins and 10 losses. The latter of which I experienced very recently and knocked me from potentially breaking through to 1300 all the way back to 1200. It was quite humbling.