What are you testing your pH with? And what are you using for remineralizing your RO water? 4.5 is very low. Adding kH will bring your pH up, baking soda can do this pretty quickly, but I recommend making these changes slowly.
Absolutely it could have. What are your Ammonia, Nitrite & Nitrate readings?
Also, what are your gH & kH readings? Generally to keep Crystal Reds you need an Active Substrate and a gH only, shrimp-specific remineralizer. What type of water are you using?
And that's on your living shrimp too?
I'd start with a salt dip for all shrimp in the tank, then I'd start looking at deep cleaning the tank and possibly even resetting it. Can you give me a panned out shot of the tank? Or maybe a few shots of the inside?
I have standpipes (overflow tubes) installed behind the HMF's in all of my tanks. So I just flow new water in with dosing pumps and let the old drain out.
Reduce feeding and the population of seed shrimp and detritus worms will lessen over time. For snails, you can drop in a piece of lettuce and give it a couple of hours, then pull it back out. Lather, rinse, repeat until the population is under control.
You're welcome! I don't have any more links, but I can say that if you don't have room for a lot more tanks then you can always start using HOB Breeder Boxes. Take the two shrimp you want to breed together and toss them in a box off of the main tank. Once the female is berried then move her back to the main tank. Take your babies, selectively move them to new tanks, and keep track of the generations that way.
If you want to breed a particular shrimp back with it's parent's then you can easily do it that way.
This is a good read for those interested in breeding out specific lines of shrimp. https://singaporeshrimps.wordpress.com/2019/12/23/all-about-breeding-tanks/?fbclid=IwAR04CFZFoHqKBOIkzRr5i9q_S-aO5FxzhqX11wXmA8l_zdmE27oPnUtpJm0
Your pH isn't staying stable because you don't have enough kH to keep it stable (otherwise it would be right around 7) and you don't have active substrate.
siphon 50-75% of your water into buckets
remove all decorations and plants
remove all shrimp
scoop up substrate and drain the rest of the water
add new substrate
add old water
add new water to level desired in tank
add back decorations and plants
drip shrimp back in to tank
I'm looking more closely at your substrate in the pics, it doesn't look like it's an active substrate. The shrimp you're keeping need a lower pH environment. You will want to swap substrate to something like Landen or Brightwell to keep things stable.