Draw a curve and imagine two downward forces at each end. Then put an upward force in the center of the curve. By tying to the center of the curve you effectively increased the weight on the curve at that point.
It's hard to break the stick just by applying force to both ends, easy when you add the upward force of your knee to the center.
Next time either tie to where the weight is or prop it up from the ground at the point of the weight.

If you have strong crotches sagging branches aren't always a problem (although you may not like the natural training results of a "weeping" fruit tree). I have an apple branch that trained itself to a downward 45° angle, curved from crotch to tip.
It's a 15+ year old tree and I think the branch did that around 3 years ago after I had given up on getting edible fruit and hadn't decided to start spraying yet so it was in a period of neglect. It was plenty old enough to be up to producing. In fact that tree is sagging more with every rain right now.
My 20yr old espaliered McIntosh produces on skinny growths that shoot out between fruits. Some of those are hanging straight down and they're smaller than a child's finger. (I think the tree is getting old or it doesn't like the size I want it to be.)

Knowing how much is too much is a live and learn issue. Like now you've learned not to tie to the middle of the curved branch.

I wouldn't write off the later bloomer. The tree is young. The late one could be self-pollinating and the out of sync only matters for looks. I would figure the person who put it together had some clue about whether they would pollinate each other.

I don't understand the concern with the bloom times. From your post it sounds as though all 3 produced fruit, so what's the problem?

Murky, I only got fruit on the two that bloomed together and I saved 3 of each type. The 3rd type had no fruit.

Yes, myk1, breaking a stick over one's shin comes to mind now that the damage is done. I get it now. : ( I guess it would have been fine if I'd just left it alone!

I hope the thinner variety will thicken with time---it sure would look silly with 1/3 tree weeping with fruit, 1/3 upright with fruit, and 1/3 with maybe no fruit.

I'll have to wait and see.

Thanks very much for your feedback & concern!

Ann

It might have been OK left alone. That's hard to say.
It could've been worse had the branch broke off the main trunk and stripped a bunch of bark with it.
Losing fruit to a broken branch sucks, but losing the tree to the same would really suck.

I've never dealt with a multi-variety tree and never thought about the different varieties growing differently. But I guess having totally different growing habits is a possibility. My 3 different apples grow differently.
You can help thicken the thin branches by heading them back (which was already done for you after the storm ;) ).