Need Help - Sick Pregnant molly with tail issues - pictures icluded

[AquaBry]

I have a creamsicle molly that is pregnant and I moved her (and a couple other mollies that are pregnant) out of my main tank (26gal) to my nursery tank so that they would stop getting so harassed by my other fish and so that I could increase their intake of frozen brine shrimp. My creamsicle molly has developed a strange whitish blob on her tail, to me it doesn't look like ick. It appears more like a whitish blob than like salt grains and one of the mommy mollies I moved over is a little nippy so i thought maybe it has something to do with that but I really don't know what this is. Any diagnostic/treatment help would be appreciated. Thanks

Here are the specs based on the "sticky".
1~Female creamsicle molly-pregnant with first brood with strange white puffy spot on tail.
2~API test kit values - pH = 7.2, Ammonia = 0, Nitrite = .50, Nitrate = 5.0 temp =79.1F
3~ 5.5 gal nursery tank linked to a 2.5 gal tank with filter housing (pic below) tank has been up for 1 week but filter tank has been running for 1 month with media from the main tank, decorations and gravel transferred from main tank.
4~main filter - Tetra brand whisper in tank filter 90 gal per hr, water bridge combines 4 pipes open with mesh bags covering intake and 1 pipe with sponge filter for intake and a powerhead pump for return/arreation pumping 75 gph between tanks and an airstone
5~3 pregnant mollies and 2 ghost shrimp
6~30% PWC daily have not changed yet today.
7~I have had the fish for over a month but transitioned to nursery tank 3 days ago. Started tanks with 75% water from main tank and 25% tap treated with Stresszyme Plus
8~everything in the tanks is pretty new kept all items in the main tank prior for a minimum of 1 week.
9~Feed mainly flake supplemented with frozen brine cube occasionally. Since moving to nursery tank have increased brine cube amount and am feeding flake only once per day. Fish always consume all food in less than 3 minutes.

Here is what she looks like.


Here is what the tank looks like (multiple pics pasted together)