Woke to some dead fish, very cloudy water, and white scum

So I woke up today to a very cloudy fish tank and some dead fish and I'm not sure where we went wrong.

Here is the situation. I'm fairly new to this. We are cycled and have been for a couple months. It's a 30 gallon tank with 3 platy, 2 molly, and 3 neon tetras and a ever growing group of snails. I have 3 small plants, but they are very small.

I checked the readings:
Ph was pretty low, it looks to be around 6, but it is usually in the 6.6 and 6.4 range.
Ammonia is in the .25 range.
Nitrite was in the range of .25 and .5
Nitrate is in the 5.0 to 10 range.

Recent things that have happened.
Initially we got one snail and it was pregnant. I keep gathering them and getting rid of them, but right now we have like 20 (we'very had as many as 40 at times)

Our platy had 5 babies 2 days ago, which I've been keeping in a hatchery, which was cleaned well with hot water before putting it in.

3 weeks ago, my daugher had the lid come off the fish food and A LOT went it. We scooped most of it out and did daily 40-50% water changes for like a week before it seemed to clear, but that hasn't been an issue in a few weeks.

Any tips, I'm doing a water change now, but I need to go to work and I'm worried about the few fish left. The baby platys are all dead, the neon tetra are dead, and I think one of the Mollies are dead too...I don't see her.

Any tips?
Anything I'm missing?

 

Welcome to fishlore!

What temperature are you keeping the tank at?

If you have ammonia and nitrite readings you are either not cycled or going through a minI cycle that could have been caused by the dead fish. You'll want to test every day and do 50% water changes until the ammonia and nitrites are 0 and stay at 0. Another option would be to do a water change and poor a bottle of TSS+ in. That should boost your bacteria population to take care of the excess nitrites and ammonia. Neons need to be in a larger school than 3.

 

If you have ammonia, your tank isn't cycled.

 

Once your pH hits below 6.4, your bb stalls, and once it hits 6.0 or less they start to die. Sounds like you had a pH crash, which took out some of your bb, and with the fish death and food issue, you started a cycle again. I would recommend some stability or TSS+ to help you along, and maybe get your kh checked to prevent crashes again.

 

^This! When you get back home from work, consider getting a GH/KH test and a bag of crushed coral/aragonite. Mollies, platys, and other livebearers prefer a higher pH, ideally 7.5 and higher, or else they'll fall apart in the long run, I believe. Neon tetras, while they do prefer more acidic, softer water, can tolerate more basic, harder water, so they can live in the same water without causing them to suffer (mine do). However, like Dragone said, it was probably the stall and subsequent ammonia and nitrite spike that killed your fish.

You mentioned that your pH was lower than normal. Do you know what it normally is? When was the last time you did a water change? I ask because KH, like Dragone mentioned, buffers pH and prevents it from swinging. Unfortunately, if the water is not replaced soon enough, I believe that the carbonate hardness is 'used up', therefore losing its ability to buffer. If you have anything in your tank that can lower pH, like driftwood/bogwood, it will finally be able to do so.

Hope this helps.