Odd Platy Behavior

[water12]

Alright I've had my 10 gallon and fish for a month now and i've never noticed this behavior from my fish before. Yesterday i did my weekly water change and since then 2 of my sunburst platies have just stayed back in a corner not really doing much at all. A couple of my red minor tetras will swim back there to check things out but won't stay long, except for one of them also. The two platies are female but only one of them looks pregnant and the male is acting fine swimming around doing his thing. If anyone can help me out with any suggestions that would be great.
Water temp: 75
Ph: normal for my water
Ammonia: 0

 

[Fishie]

Some platys will hide when preggers mine did. Did you add anything to the tank recently? What about nitrites and nitrates?? Do they look like they are getting bullied?? Also do they look okay??

 

[water12]

The nitrite levels are at 0 and the nitrate level is at 39 ppm
I just find it wired that they suddenly started acting like that in the last 24 hrs. They've started swimming around more but are still sticking to the bottom of the tank

 

[Fishie]

The nitrite levels are at 0 and the nitrate level is at 39 ppm
I just find it wired that they suddenly started acting like that in the last 24 hrs. They've started swimming around more but are still sticking to the bottom of the tank

I would do a PWC and lower your nitrates you want them lower.