Gold Mickey Mouse Platy

 I have had 3 gold mickey mouse platys since the day I got the fish tank which is going on 6 weeks.  recently I would say within the last week, I noticed they have been hiding in a house I bought for them. they pretty much stay there all day.  the one has come out more so, but the other two don't. I just shined a light in the house and finally my big one came out for a short time, and now has returned back. I noticed that my big Platy has some red on the top fin and stomach area, I haven't seen the third one come out at all. I have enclosed a picture, one showing the little of the others and my big Platy. this is unusual since they never really hid before. 

They are probably still finding out their home if you just put in some new decor! It may be stress

The red areas appearing on the male could be just his markings returning, because when fish are stressed their colours fade

If you added the fish six weeks ago and set up the tank around the same time, you're likely still cycling which can cause lethargy, shyness, and reddening of the gills.
 
What size tank is this? What are your water parameters? Any other tankmates?

 we Are cycled,  it's a 48g water was tested today no ammonia, no nitrites, and no nitrates.  tank mates include  diamond tetras, red minor tetras, neon tetras, guppies, mollys, platys, catfish, pleco, black skirt tetras 

new decor was placed  around 3 weeks ago. I have changed decor around  tho, to Remove what I thought to be boundary issues. 

 I wonder if there is a bacterial infection spreading thru the tank.  in this past week I have bought several fish from petsmart that have died.  I have  had quite a bit of changes between adding fish, and removing fish 

They could be harassed as well. Odd that you haven't any nitrates. What species of catfish, by the way? What numbers for the rest of the fish? Sounds very tightly stocked.
 
Very well could be an infection, but I would start off with some water changes. They never hurt and may make your fish a little more comfortable.

How did you go about cycling the tank?

 I have a 1 Cory catfish, 1 pleco, 3 guppies, 3 black skirt, 4 red minor, 2 diamond, 3 gold mickey, 2 blue Platy, 2 white Platy, 2 green Platy,  2 yellow /Black Platy, 1 red Platy, 1 Dalmatian molly, 2 balloon molly 1 snail, 5 neons 2 baby snail

I started with a 20 gallon fishtank, I bought 2 Dalmatian molly,  5 platys,  2 black skirts, 3 neons... after the tank cycled completely, I transferred to a 48 gallon bow front tank.. then added more. water changes every week, sometimes 2 times a week. 

I went to the stores almost on a daily basis to get the water tested. anytime any of the parameters spiked I did a 50% water change. I have purchased my own kit that I am still waiting for... it's better and more cost efficient to do it myself, since I wasted all of that gas to get it checked. I just had it checked yesterday, I was told water was perfect so that's when I added 5 fish yesterday. 

my original Dalmatian molly died, my black skirt was being nipped and was killed by my dwarf gourami. I got rid of the dwarf gourami.  I replaced those 3 fish with 2 neon, Dalmatian molly and 2 guppies and black skirt..  the guppies didn't work out so I took them back, and the Dalmatian molly died. that black skirt died I replaced that one. bought 2 red Minor  tetras. 1 died. these  fish were all from petsmart. I was also told to use melafix, I did for 3 days.