2 Dead guppies in 24 hours

A week and a half ago I bought 4 female 2 male guppies 3 platies and added to 5 Zebra Danios. Tank details below. In the last 2 days I've lost 2 guppies. They literally went from swimming and eating to dead. The only thing I've done differently in the last 2 days is I turned off the pump to feed so I could properly watch them eat. When you turn it back on it's quite a strong initial shot out the nozzles. If one of them is in front of the nozzle could that shock them? It's my first community tank.

32.5 gallon Fluval flex
78 degrees
API master test kit
Ammonia 0
Nitrites 0
Nitrates 5ppm
Ph 7.2
Food: Tetra tropical flakes 2X/day
Frozen brine shrimp 2X/week
Weekly 10-25% water changes with gravel vacuum
Planted
Fully cycled

The day I brought the guppies and 3 platies home I found a zebra Danio that was having problems swimming. I removed him and put him in the hospital tank. It looked like a swim bladder issue or an injury that affected his tail. He was swimming nose up. I had started feeding the Danios Mini pellets a.few days prior and I'm guessing it caused him problems. No idea. The only thing I'm confident with is the tank water. I've been testing regularly and keeping up with maintenance. The guy who was struggling was the smallest of the bunch. No issues with the other Danios so far
I did a large water change (50%) after removing the sick Danio, before adding the new fish. I had also just done the weekly water change (~25%) the day before.
I should edit the nitrates - it was under 5ppm but it wasn't 0.

 

Very doubtful you've done anything wrong. Sadly it's just a common experience with store bought guppies. Changing environments is a bit of a shock and most guppies in the store are line bred which just doesn't give you really strong guppies so they just die easily. Whatever sickness they can catch, they usually will. My tank bred mutts and hybrids live multiple times longer than almost anything I've ever bought. Once you get some fry from the ones you have and you get a generation or two of your own stock, they'll be much stronger and less prone to sickness.

 

Okay now 2 zebra Danios are dead and one of my platies is hanging out in a corner. What on earth is going on? Here's a picture of the Danios. The one has red gills. I just did a WC yesterday. They go from active to slower to dead in a very short period of time with no signs of illness. Parameters are good. I don't know what to do. Would hand lotion or sunscreen do this? There's one day where I may have forgotten about rinsing off my hands when the first guppy died. I'm starting to think that the first guppy may have died from whatever causes and I didn't even think about it, I just grabbed the net and got him out without rinsing my hands. We were getting ready to go to the beach and I'd just put sunscreen on.

 

Those guppies could've been weak already before you bought them. It's already mentioned overhere. It's sad that it has happened but it's not abnormal.

 

Just did another water change - pretty sure I got sunscreen in the tank the other day so it should all be fine now. Down 3 guppies, 2 danios. The LFS will replace the guppies. The danios I've had a long time so I'm not very happy about that. Platy's are fine. I checked absolutely everything in that tank. There's no sign of disease in any of the fish. Fasted them yesterday in case they're just overfed. I added an air stone and buffered the outflow so will just leave things alone for a week and hopefully all is okay. I don't know how to assess oxygen but I have decent water movement and I added an air stone to be safe. I'm open to any and all advice. Thanks everyone for your help