Your female has a "white looking thing hanging out her anal"?
Do you mean this as her breeding tube came out? or does it look as if she's pooing white feces?
If she's pooing white, that's not a good thing. That means internal parasites.
Just asking to clear that up.
Also, what do you mean a Kenny fish? What's the proper name of this fish?
And what kind of Plecostomus (Pleco for short) do you have? Is it a bushynose, or another type of smaller species of "suckerfish", or is it just a Common Pleco?
If it is a Common Pleco, it will need to be rehomed eventually down the road, because they can grow up to 12 inches in length.
Convicts will do fine with a high quality fish flake food, frozen blood worms, frozen brine shrimp, or small fish pellets.
If the convicts start to spawn, it will probably become noticeable to you because they will become more aggressive to all the fish in your tank, and your female may develop a peach/orange colored belly.
When my convicts layed eggs, the female dissappeared for a few days straight, she was hiding/laying her eggs and hatching them.
Then all of a sudden, she appeared with tons of small babies about the size of a grain of rice.
They are excellent parents and will defend their babies. They may even become overly aggressive to your other fish, so be careful...
I have a 90 gallon aquarium, and while my convicts had their babies around, they sure nipped up some of my other fish's fins (mind you, the fish they nipped up are 3 to 4 times the convict's size)
a 7 inch Severum, a 6 inch Blood Parrot, and my 4 inch Oscar all got nipped on.
I had to put my Oscar into a hospital tank for him to heal, he got nipped up so bad.
You can put some cave-like decorations into your tank and some flat rocks for the female to lay her eggs.
She could either choose a cave to go into and lay eggs inside on the wall of the decoration (like mine did) or she could lay all of her eggs out in the open on the surface of the flat rock.
Sorry I typed so much, hope I help!
