Help My Guppies Keep Dying

so I have a 10 gallon glofish tank with a 50 watt heater an adjustable 20 gallon filter (I have a 20 gallon filter because I had to much algae growth) 4 plants and 1 ornament. My tank currently holds 3 glofish tetras, 2 corydoras(Cory catfish), 3 snails (1 mystery snail and 2 nertile snails) and 1 female fancy guppy. I just added in the corydoras 2 days ago and there doing perfect! My problem is I had originally had 5 female fancy guppies (that I got a week ago) and they all seemed healthy but then 2 all the sudden died so I tested my water and it was a high PH level but I fixed that day. The next day another fancy guppy died that seemed healthy the day before. And the day after that another one died (today) I still have that fancy guppy ( of course in a bag out of the aquarium). I have one fancy guppy left now and I can’t tell if it’s bloated or pregnant or if something is wrong with it. Here are some pictures




Any help is appreciated

 

so I have a 10 gallon glofish tank with a 50 watt heater an adjustable 20 gallon filter (I have a 20 gallon filter because I had to much algae growth) 4 plants and 1 ornament. My tank currently holds 3 glofish tetras, 2 corydoras(Cory catfish), 3 snails (1 mystery snail and 2 nertile snails) and 1 female fancy guppy. I just added in the corydoras 2 days ago and there doing perfect! My problem is I had originally had 5 female fancy guppies (that I got a week ago) and they all seemed healthy but then 2 all the sudden died so I tested my water and it was a high PH level but I fixed that day. The next day another fancy guppy died that seemed healthy the day before. And the day after that another one died (today) I still have that fancy guppy ( of course in a bag out of the aquarium). I have one fancy guppy left now and I can’t tell if it’s bloated or pregnant or if something is wrong with it. Here are some pictures
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Any help is appreciated

Since you just bought them, I think some possible reasons might be disease or stress. Also, seems like the glofish tetras are colored black skirts, those need a group of about five and corydoras also do better in bigger groups.

 

Welcome to Fishlore! You've come to the best place for help. There are so many knowledgeable people here!

So I can certainly see multiple things that could be possible issues.

The main issue I can see is that in your profile you said you did not know of the Nitrogen Cycle. <--- Click these words as it'll explain a lot of what you need to know. I'm guessing you probably don't know the tank parameters.
Secondly, adjusting pH for no particular reason is very deadly to fish and chemically altering can cause swings, which will certainly kill fish. Unless your pH is very low, like 6.0, it doesn't need to be adjusted. Fish adapt to the pH and live perfectly healthy.
I would also like to politely point out that you are unfortunately overstocked in a 10 gallon. The Glotetras and Cories really are more suited for a 20 gallon tank, though that certainly doesn't kill fish. However, putting fish in a tank that's overstocked and crowded can cause stress which makes fish more susceptible to disease and illness. They are both also schooling fish that really thrive in groups of 6+

My main advice is the read up on the Nitrogen Cycle. Personally I'd recommend buying a bottle of Tetra Safe Start and following the instructions on the bottle. Your tank needs to be cycled in order for fish to thrive.

 

Welcome to Fishlore! You've come to the best place for help. There are so many knowledgeable people here!

So I can certainly see multiple things that could be possible issues.

The main issue I can see is that in your profile you said you did not know of the Nitrogen Cycle. <--- Click these words as it'll explain a lot of what you need to know. I'm guessing you probably don't know the tank parameters.
Secondly, adjusting pH for no particular reason is very deadly to fish and chemically altering can cause swings, which will certainly kill fish. Unless your pH is very low, like 6.0, it doesn't need to be adjusted. Fish adapt to the pH and live perfectly healthy.
I would also like to politely point out that you are unfortunately overstocked in a 10 gallon. The Glotetras and Cories really are more suited for a 20 gallon tank, though that certainly doesn't kill fish. However, putting fish in a tank that's overstocked and crowded can cause stress which makes fish more susceptible to disease and illness. They are both also schooling fish that really thrive in groups of 6+

My main advice is the read up on the Nitrogen Cycle. Personally I'd recommend buying a bottle of Tetra Safe Start and following the instructions on the bottle. Your tank needs to be cycled in order for fish to thrive.

Ok thank you for your advice! I will certainly read about the nitrogen cycle. I was actually planning on getting a 20 gallon live plant setup soon and once I get that tank established I will get more tetras and corydoras.

Since you just bought them, I think some possible reasons might be disease or stress. Also, seems like the glofish tetras are colored black skirts, those need a group of about five and corydoras also do better in bigger groups.

Okay thank you for the advice!

So I read over the nitrogen cycle and it turns out I am familiar with it I just didn’t know it had a certain name

 

I would recommend getting the API Freshwater Master Test Kit. It allows you to monitor your Nitrite, Nitrate, and Ammonia.